May - I have to say that even if he deletes all her contact information, if someone wants to find someone, they will. FB, Instigram, Twitter. As long as he has her name, he will find her. I'm not saying he will. I'm just saying this type of thing takes self motivation. And there's a reason it's called 'self' motivation. He controls it. Not you. Trust him or don't trust him. But you have to commit to the trust. You have to not assume the worst every time he looks at his phone or is gone a little too long.
I have read a lot of stuff about divorce and pilots - the fact that when they are away they are kings of their little kingdom. A continuing stream of people who look up to and respect them and follow their every word. They are in charge. And whilst they are away, we establish routines, bedtimes, school runs, taking the rubbish out, getting the groceries, calling in repair men. So use to being in charge, they come back and feel lost, no-one is deferring to them, or even worse, they come back and get hit with four days worth of problems at once "the dishwasher's broken" or "X did this in school".
I understand know how hard that must have been. Throw in unconscious resentment on my part - he gets to go away for four days and leave me at home with two young kids, his job is viewed by everyone as more amazing (god I hated how everyone fawned on him when he told them he was a pilot) even though its my job that pays most of the bills and what you get is him feeling emasculated when he gets in.
I wish I could talk to him about this now. But it is too late. It is not too late for you.