A modified Gulfstream II flying as a Shuttle Training Aircraft for NASA was 13,000 feet above Florida recently when parts of its thrust reverser went missing and splashed into the Banana River. The reversers are part of a retrofit that helps the GII mimic the Shuttle's steep descent profile. An astronaut and two pilots were on board when the parts fell off in early December, and the crew aborted the mission and made a safe landing, Florida Today reported on Saturday. NASA's fleet of four modified GIIs was grounded after the incident and the fasteners for the reversers were beefed up. After that, test flights checked out OK, and the fleet was back to normal by Jan. 12. A NASA safety panel (no irony intended) had raised questions about the safety of the aging fleet of training aircraft several years ago, Florida Today reported.