debbie hearseman is chairman of the ntsb. >> we believe there are certain air spaces that are challenging. we investigated one involving two news-gathering helicopters in phoenix and we made recommend aches about technology, proximity awareness of traffic. alerts. we made some recommending as about technology might improve it. we have seen -- >> traffic collision avoidance systems? >> right. awareness for large aircraft. >> see how it pops up on the screen? traffic. somebody coming at us. he's 600 feet higher than us. >> back in our helicopter, there is technology to pip point nearby aircraft. it is not mandatory. >> see the helicopter all the way up there? he's much much higher than and we know this because of the device. >> some experts have recommended that an in areas such as the hudson river, planes and helicopters be required to fly at different altitudes. of the lytle -- after the lytle crash, the faa banned all aircraft without special permission from aircraft traffic. that ban did not apply to the hudson just two miles across town. >> we will continue to look for all of the aircr