opportunity to act now and establish a production cutoff date of december 31, 20189, after which tier viii knox standards will apply to newly-manufactured aircraft in lieu of the tier vi standards. nescom intends to submit more detailed comments before the close of the record, but we thank you very much for the opportunity to be here today. >> thank you. my name is andres restrepo, and i'm an associate attorney with sierra club's environmental law program. sierra club was founded in 1892 and stands today as one of the largest and most active grass roots environmental organizations in the united states. with over 2.4 million members and supporters as well as 64 affiliated chapters nationwide, the club works to secure a cleaner, healthier and more sustainable environment for today's world and for future generations alike. one of the club's most urgent goals is working to curb the effects of climate change, and we strongly advocate for steep and immediate cuts to greenhouse gas emissions from all sectors of the economy. unless governments act now, we will be unable to avoid the worst impacts of cl