hazu and past tense (WAS supposed to)

Hello again!

I know "hazu" can mean "ought to", "should be" or "supposed to" when added to a base 3 verb. I'm wondering how you say someone WAS supposed to do something. In other words, hazu in the past tense. I think hazu can be used with some conjugated verbs like ikitai. Can they be used with past tense? "ikimashita hazu"? "itta hazu"? Can these work? If not, how do I go about doing it?

Here's an example sentence:

Last week, a friend of mine was supposed to go to Egypt by plane.
(FYI: In the end he couldn't as the flight was cancelled.)

先週, 私の知人は飛行機でエジプトに行きましたはず.

This sentence really doesn't feel right to me. I'm sure I've got it wrong in at least a couple of places. :sorry: I've placed the 飛行機で before the エジプトに because of the fact that he is going by plane is more important than where it is he is going (although I think the sentence would still make sense the other way round).

I'd love some corrections and advice to help me learn, especially regarding using hazu properly. :?

It should be 先週、私の知人は飛行機でエジプトに行くはずだった. はず can't be used with polite forms. Plus, エジプトに行ったはず（だ）means "should have gone to Egypt."

As usual, it seems very obvious once you've shown me!

Thank you very much. I really appreciate it.