Thanks for the comments and the links, grudzio. Good to know we can do it without dealing with integrals.

BTW I wrote a draft trying to put order in ideas about flying phyisics. I'm sure it has a lot of mistakes (including bad English redaction ) but it can be a "start point". Read it and put here your apportation.

The link to the document: http://www.burdjia.com/personal/flight.txt