United Grounds 96 Planes Airline behind on operational checks on required changes By Mary Papenfuss, Newser User Posted Feb 16, 2011 2:42 AM CST 0 comments Comments United temporarily grounded 96 Boeing 757 for maintenance checks. (AP Photo/The Salt Lake Tribune, Steve Griffin, File) (Newser) – United Airlines is temporarily grounding 96 Boeing 757s while it conducts maintenance checks. The move forced the cancellation of 15 flights and caused several delays yesterday, with more cancellations possible today, AP reports. The planes were grounded when it was discovered operational checks had not been completed on modifications to on-board air data computer systems required by the FAA in 2004, said a representative. The modifications involved installing new circuit breakers, relays, and related components, and making wiring changes in and between the flight deck and main equipment center.