this is "nightline." >> tonight, psychology of a killer. new clues coming to light about the youngpilot who crashed the german wings plane. a doctor's note. an unfilled prescription. painting a picture of a troubled man hiding illness from the airlines. with search teams scouring the wreck an could this tragedy have been prevented? do you need a wolfpack? >> i just added two more guys to my wolfpack. >> somewhere between college buddies and husbands with kids some men are finding they've lost their friends. now there's an app for that. and, rocket man. that american astronaut blasting off today for a history-making year-long mission in space. and how his famous twin brother is helping out from right here

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disturbing new detail emerging about the pilot who investigators believe deliberately crashed a german jet, killing 149 innocent people. the young man apparently hiding a dark secret with concerned medical professionals excusing him from duty on that fateful day. why did he show up anyway? abc's chief foreign correspondent terry moran is on the ground with the latest. >> reporter: deep inside the craggy ra venous of the french alps recovery workers sifted through twisted metal and scattered debris. this devastating carnage prosecutors now say was deliberately caused by 27-year-old copilot and andreas lubitz. after searching lubitz's apartment prosecutors say it's clear the copilot hid a dark secret. investigators found a note from a doctor determining lubitz was too sick to work on the day of the crash, and prescriptions for medications, also trashed. prosecutors summing up the

shocking findings lufthansa didn't know. "the deceased hid his illness from his employer and colleagues." prosecutors say lubitz locked the pilot out of the cockpit, programmed the descent and intentionally slammed the plane into an alpine ridge at 400 miles an hour on tuesday, killing all 150 on board. just two weeks ago the copilot was being treated at a hospital for conditions unknown. a person familiar with the investigation told "the wall street journal" that lubitz was being treated for depression and was worried that the airline would find out about his illness. german media reporting that the copilot suffered burn-out or depression, leading to an extended absence during his pilot training in 2009. christine negroni, aviation safety expert, said she was at the same arizona flight program as lubitz five years ago. >> it is not unheard of for pilots to keep from their employers medical conditions that they feel might ground them. it's one of the few professions

where if you are ill, certain illnesses are not tolerated and you're not allowed to fly. >> reporter: she didn't know the copilot personally but says the program was rigorous and lubitz like all students there had to be specially selected for the extensive training. >> this is a group of fresh-faced kids. i mean, you know they're all in their 20s. they're starting off -- they've wanted to be pilots. they're seeing they're going to go to work for a prestigious european company. they're going to be flying around the world on big airplanes. they were excited. >> reporter: by all accounts lubitz appeared to be a quiet and capable pilot at germanwings, the subsidiary of lufthansa. he never shows signed of inner turmoil. he grew up in montebauer germany, and by most accounts lived an ordinary life. at home last night where the shutters were closed he started at a flight school in his hometown. these are the gliders at the local flight club, packed up for winter. it was here in these that

andreas lubitz first discovered his love of flying. >> this was a normal young person. normal young person without any -- any extras any things which would tell us that something's wrong. >> no red flags? >> no absolutely not. absolutely not. >> somebody who loved to fly? >> absolutely yeah. >> reporter: lubitz was an avid runner, the picture of health ask youth. investigators say lubitz's secret illness turned him homicidal. in the 24 hours before the crash he left his apartment in dusseldorf, neighbors say he shared it with his girlfriend, two names on the buzzer. he went to the airport, flew to barcelona in the morning, directly over the same place he would crash that plane hours later. >> i don't think there's any doubt that this copilot was fully qualified to be able to fly the airplane. that's not really a factor. apparently lyly it doesn't have any bearing whether they have the propensity for taking it down, a malice murder suicide situation.

>> reporter: the claim lube byes crashed the plane raises questions how airlines screen pilots for mental health issues. while in flight school lubitz was cleared by the federal aviation administration of psychological problems. but robert novin, seen why are aviation medical exercise, says the initial psychiatric evaluation is not often rigorous. >> there's no real guideline except for general observations and impressions. it's all self-reporting. so it's partially my observation and partially what they're willing to tell me. >> reporter: if there's indication a pilot is suffering from substance or mental health issues they are subject to additional rigorous psychiatric screening. >> if i have a case that's referred to me i'm going to meet with that individual to evaluate, i'm going to gather as many facts as i possibly can. this is going to be through a pretty extensive face-to-face interview with the valuee. i'm going to review all mental health records current and past. >> reporter: even if a pilot is suffering from a disorder like

depression or anxiety, it's up to them to seek help or their colleagues to report it. >> when an individual doesn't self-report, and if there aren't any overt signs amongst co-workers or airline personnel, if there's no legal involvement, it's pretty difficult to be able to identify the presence of a condition. >> reporter: deliberate crashes of commercial airplanes are extremely rare. but when underlying conditions and emotions enter the cockpit, there can be devastating cons consequences. in 1999 an egypt air copilot downed the 767 carrying 217 into the atlantic ocean, saying "i rely on god" as he steered the plane down. and in 2013 a mozambique airlines pilot locked the copilot out of the cockpit before crashing the plane to the ground. and now this. as investigators are still putting the pieces together. so far, there are no signs of a suicide note or any motive. they continue to remove items

from lubitz's apartment, looking for anything to explain why and how he could have deliberately committed mass murder and suicide. many european airlines are taking steps to prevent this from happening again, now requiring two crew members to be in the cockpit at all times. but that is no solace for the families who want their loved ones to be identified and brought home. for "nightline," i'm terry moran in montebauer, germany. up next, are you a dude who needs a new crew? that's where the wolfpack comes in. later on night line the astronaut launching himself on a mission to make history. and clearer skin. this is my body of proof that i can fight psoriatic arthritis from the inside out... with humira. humira works by targeting and helping to block a specific source of inflammation that contributes to both joint and skin symptoms. it's proven to help relieve pain,

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so, if you're a man or you have a man in your life tell me if this sounds familiar. college friends, scattered. co-workers, all seem to be married with children. on friday night, the guy's looking not for love but for bromance. a new app is helping guys seeking company for the man cave. but will they actually go online and search a friend? abc's nick watt gave ate whirl.

>> this is the app. >> reporter: we didn't know each other till a half hour ago. now look at us. sharing injury stories. >> get back on the field. if your leg's not broken. >> reporter: good times. this might be the salvation of modern male heterosexual friendship. >> straight men are basically the least socially evolved humans. >> absolutely. yes. this is needed for straight guys. >> reporter: it's an app called wolfpack. >> whoo! >> reporter: yep. it makes that noise. so here's how it works. you list your hobbies and interest. >> select all that apply. sports. rugby. why don't they have cricket on here? >> reporter: then either attend a posted event or create your own. basically a group mandate. mine is drinking beer at ye olde king's pub in santa monica. >> it's changed in the past ten

years. >> reporter: showing off our tattoos. >> oh my god. >> black and white. >> reporter: brain child of movie producer current developer of the most expensive homes in this country he was inspired by a recently divorced friend. >> a lonely guy that lost track of all his buddies because he was married for 20 years. when he got divorced he had nobody to do anything with. >> reporter: women are better at friend stuff than most men. did you see "i love you, man"? >> i have no idea i think his best friend is his mom. >> ew! >> no no not like that. >> i've got to get some [ bleep ] friends. >> i kind of feel badly for men. they were given the message, if you're very revealing or if you are very intimate then you're being girlie. you're being vulnerable. and so even though men may want to have that kind of connection with another man, they've been raised to think, oh that's not

where we should go. that's not masculine. i'm not allowed to do that. >> i think the women, they keep in touch, they have a group of women that they stay close with. if that ever happens that they break up or something changes in their life, they have somebody to go to somebody to talk to. >> part of the appeal of this is my wife and i share zero interests. she doesn't like rugby. she doesn't drink beer. we actually -- actually my wife and i actually have nothing in common. so maybe this will be good. take the pressure off her fading interest in stuff i talk about. >> reporter: 4,000 users so far, mostly in l.a. john, rob and david met at a sports bar event to watch the clippers. >> what, you can't find friends the normal way by meeting people? >> what does that mean? >> we're meeting people. >> like online dating. >> reporter: yeah, okay. no stigma to online dating anymore. >> guys want to be in packs. that's like -- it's more natural. >> men are feeling more comfortable saying, hey, i have

a need for male friendships too. i'm not so different from my wife who gets to hang out with her girlfriends and do lunch. she seems so happy after she comes back from a day with the girls. guys want that too. >> we started talking over the app and found each other, then we just sat and watched the game, had beers, enjoyed the game. >> reporter: is john being a little -- "planes, trains and automobiles"? >> see that game, hell of a game, bears got a great team this year, they're going to go all the way. >> we were very cognizant to make this a manly site. >> and practice >> yes. >> i don't want to embarrass anyone but you quite like each other? >> yeah. >> reporter: they won't admit it but they like me enough to show up at my king's head shindig. pretty good turnout, right? i'm stoked. it is clearly men in their 30s looking for bromance.

>> it's a point in life where a lot of my friends are married, having kids. and nobody wants to do anything anymore that's even remotely fun. >> reporter: kevin was married ten years, recently divorced. >> i used to go on a bowling team. the bowling team was literally my brother-in-law and his uncle, you know. another co-worker of hers. at some point you had to slice that out. >> right right. >> fill in the holes other ways. >> how many friends have i lost over a girl? mutual friends? >> oh my gosh. so many friends. >> we've all been there. >> reporter: with wolfpack you can pick and choose. >> i'm like dude i'm never going to see you again. there's no harm. >> i tried one of the other ones too. it was so broad that there would be people there but not a whole lot in common. i thought, i like to hike i'll go in a hiking group, make new friends. no offense but i get there and there's like this 65-year-old woman.

awesome that she hikes, more power to her. we're not going to go hang out afterwards, you know? >> i love how technology is giving us permission to venture into new areas that can be healthy. and so it's great that men are realizing they have this need to connect with other men. >> reporter: here we're bonding over guy stuff. beer and bar snacks. "the hangover" is more profound than i dared believe. >> six months ago, when doug introduced me to you guys i thought, wait a second, could it be -- and now i know for sure. i just added two more guys to my wolfpack. >> reporter: i'm building my own pack. rob, john, dave and i are meeting soon for deep fried -- you wouldn't get it. it's an inside joke between bros. i'm nick watt for "nightline," whoo! ? santa monica. up next what a trip. can this astronaut who just arrived tonight at the international space station pull off the longest nasa journey

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an american astronaut on a historic mission radioed back to nasa late tonight from the international space station after leaving earth just hours ago. but could you imagine spending a year with limited human contact in very tight quarters, all while floating in space? hires abc's david kerley. >> engines at maximum thrust. >> reporter: a liftoff making history today. astronaut scott kelly taking off for a year-long mission in

space. it's the longest expedition nasa astronaut has ever undertaken. hours ago, arriving safely at the international space station. >> now below 50 meters. >> you're putting yourself at risk. we've never done this before with an american a year in space. it can mess up your eyes it can mess up your heart. it can mess you up. >> there are risks. i'm willing to accept that for what we're going to learn from it. >> reporter: scott, part of a nasa study on whether the human body can survive a trek to mars. but he's not alone on this mission. >> we need to figure out how people are going to live in space for really long periods of time. especially if we want to send somebody to mars or maybe want to send people to -- maybe one day build a base on the moon. >> reporter: that is mark kelly, former shuttle commander, husband to gabby giffords twin brother of scott, and an important part of this mission by staying on earth. >> you get the easy part of this. >> the really easy part. >> reporter: his matching genetic code making him the perfect subject to measure against scott. for nasa scientists this mission

could provide a gold mine of data. looking at the effects of how physical strain radiation exposure muscle deterioration, and psychological pressure, will affect scott. >> you once told me that when you came back we might be the same age. >> reporter: a real-life version of "interstellar." leaving earth is far from easy. >> what do you expect to miss the most? >> the human connection. the connection you have with people that you care about on earth. >> you still miss the variety that you get by you know being on earth and the people that are important to you. >> reporter: but for the kelly brothers, the rewards outweigh the risks. >> you both have the chance of actually paving the way to mars. >> that's one of the things that makes it exciting and something i'm really happy to be a part of. >> reporter: tonight, the first night for scott kelly on the international space station. >> contact and capture confirmed. the one-year crew has arrived. >> reporter: the kelly brothers' space expedition just getting started.

for "nightline," i'm david kerley in washington. >> another giant leap for mankind. what must haves would you pack for a year in space? head to our "nightline" facebook page and let us know what you'd pack in your bags. tune into "good morning america" tomorrow and as always we're online at abcnews.com. good night, america.

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