READ: Qatar Airways is the world's favorite airline.  For instance metals contract at different rates, while lubricants may lose their viscosity, creating wear issues for moving parts. One of the tests is to shut down the aircraft for 24 hours and then do a cold start. The scope of the trials include: Engine and APU start after the cold soak; thrust-reverser tests with snow; verification of systems behaviors at extreme temperatures; and rejected take-offs. Boeing has announced a slowing of the 777X program to accommodate certification changes and customer requests for delayed deliveries due to COVID. The company also advised that there could be a cutback in orders of up to 40 percent to just 191 jets in a 10-K filing. The company’s website lists 309 firm sales but the latest delay to the jet’s debut now set for late 2023 has given some airlines the option of exiting the program and over 100 orders are at risk. The COVID pandemic has reduced demand for larger twin-aisle aircraft with it not expected to return till late 2023 or 2024. The Boeing 777X once described by Emirates President Tim Clark as a peach has a rosy future. It has been ordered by blue-chip airlines such as Emirates, Qatar Airways, Etihad Airways, Lufthansa, Singapore Airlines, Cathay Pacific Airways, British Airways, and All Nippon Airlines. It was launched at the 2013 Dubai Air Show, with 259 orders and commitments for US$95 billion. The launch was the largest commercial aircraft launch by dollar value and Emirates led the way with orders for 150, with Qatar Airways for 50, and Etihad Airways for 25. Earlier Lufthansa committed to 34 aircraft. Total orders are now put at 309 after Emirates decreased its order by 35 replacing them with 787s but the Boeing filing indicates a loss of a further 100 aircraft orders. It is rumored that Emirates will swap more 777Xs for 787s. The current backlog is listed as ANA 20, British Airways 18, Cathay 21, Emirates 115, Etihad 25, Lufthansa 20, Qatar Airways 60, Singapore Airlines 31, and Unidentified 10.