Is what my employer did legal?

I signed a contract with an airline in February. In the contract it states that I'm not allowed to work anywhere else, not even part-time. They delayed my joining date due to the coronavirus. Every week, they send me emails to tell me that they're committed to make me work. Yesterday, they sent me an email to terminate my contract. So I waited 4 months with no salary and no possibility to find another job, and at the end they just fired me with 0 compensation. Is this legal?
Is what my employer did legal?
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