When Donna is on her very first flight with Sierra Air, her hair is piled up in a 'big' hairdo with a ponytail. When the flight is over, and Co-Pilot Steve is talking to her, her hair is perfectly straight.
When Christine makes the "assess the window" comment, she is wearing the long sleeve teal shirt, but in Donna's reaction shot she is wearing the sleeveless teal shirt. When it's Donna's turn to "assess the window", she is wearing the long sleeve shirt. The class dresses identically throughout the training course.
When Donna gets the results of her re-taken exam, John Witney hands her a folder. When the camera cuts to her, she is holding the folder but when it returns to John, the folder can be seen on his desk. When the camera cuts back to Donna, she is still carrying the folder as she leaves.
When Christine turns back around to confront Donna regarding the Ghost Rider that was on her flight who caught Christine stealing from the airline, there is a mic visible at the bottom of the screen for a few seconds near her chain belt she is wearing.
At the time when Christine and Donna are fighting in the forward cabin of the aircraft, Donna is apparently the only member of the cabin crew onboard. The first passengers can be seen ready to board the aircraft at this point, and during the boarding stage all members of the cabin crew would be in the cabin.
Donna is flipping through her mail, which is addressed to her with an address of Cleveland OH 44054. However, 44054 is not a Cleveland zip code. It corresponds to Sheffield Lake, which is a suburb of nearby Lorain OH.
When Donna qualifies she gets a position flying for Royalty Express and is based at Cleveland International, she is seen working on a propeller-type aircraft, yet at the end when she has qualified as a airline captain the aircraft is a 757/767 jet, but her passenger announcement still quotes it as being Royalty Express.