If you want something done, do it yourself. Is it true?

If you want something done, do it yourself: is it true? Talking about ops and crew software management, there are two different streamlines in airline IT departments at the moment: the first one supports and applies the theory that the software should be developed in-house, following internal needs and specifications; the second one goes in opposite direction: Airlines should select one or more vendors and purchase software off-the-shelves from them, with some customization if needed.