Excel maintains a recovery file of your open document. If it crashes, you can reopen Excel and will likely recover most if not all of your data. You are far mor

Excel maintains a recovery file of your open document. If it crashes, you can reopen Excel and will likely recover most if not all of your data. You are far more likely to corrupt data by keeping the files (primary and recovery) open in a program that is in a known-bad state. If software crashes, it can simply be rebooted. I can't get the actual requirements for airplane control softward without paying hundreds of dollars. However, I would imagine that a reboot finish quicker than a pilot could open the manual to the "negative altitude indication" section.