Why are internal UI deadlines necessary to use the FASTLANE sytem?
For various reasons, NSF FASTLANE proposal elements may be completed incorrectly, and it often takes more than a day to get things straightened out. So if an NSF FATLANE application were attempted at the last minute and something went wrong, the deadline would be missed. NSF will extend a deadline only for errors caused by an NSF FASTLANE glitch or a natural disaster.