The New York Post reported Sunday that, according to Federal Aviation Administration regulations, Sullenberger will only be allowed to pilot airline flights once he has completed three takeoffs and landings.
The takeoffs and landings must all be completed with a 90-day period, but can be conducted in a flight simulator or a real airplane.
"He's going to probably lose his 90-day currency, so he'll have to come back and train in the simulator," said Capt. James Ray, a US Airline Pilots Association spokesman.
Sullenberger, 58, said following his successful Hudson River landing on Jan. 15 that he plans on returning to US Airways at some point.
His union informed the Post the pilot's next scheduled flight is sometime in March.