Hes using a very mean type of manipulation. Why would it be so hard for him just to accept he doesnt like flying?
Now hes probably working himself up into a jealous state about you having 'holiday enjoyment' on your own.
Why dont you pretend to go along with his new offer of going on holiday with you - but also continue to plan your girlie holiday. If you cant afford 2 holidays you will have to trust your instict that he is BSing you. But if you could afford 2 holidays at a pinch, then go right along with his 'we are going on holiday together' plans but say you promised the girls. If its another of his tricks you still get a holiday, but if he finally puts his money where his mouth is then you get 2 holidays!