Oh come off it. There is no cloud cover, the earth is a flat plane, the flight path is level, and we're assuming standard temperature and pressure. Lightspeed m

Oh come off it. There is no cloud cover, the earth is a flat plane, the flight path is level, and we're assuming standard temperature and pressure. Lightspeed may be neglected, and the observer is at rest with regards to the earth and atmosphere. The jet is making noise. Pedantic people who can't do back-of-the-envelope calculations due to "underspecified" problems piss me off, partly because I used to be one of them. ;-)