With all due respect, people who ask a question like this are usually the unwitting target of a romance scam, where someone who has been wooing them online suddenly wins an international contract and must leave the country for work purposes before he can meet up. The so-called romance continues to grow after he is abroad, but then suddenly, talk of love ceases switches to talk of money -- yours. He has a so-called emergency and can't complete his contract and won't be allowed to leave Turkey unless you give him a large loan which he will pay back when he's finished the job and comes home to you. Except, if you pay it, he'll need more money, and more, then more, then more, then more. And he'll never get anywhere near a plane because the whole scenario is only a pretext to allow him to steal from you.
If that's the scenario you're dealing with, you're being taken for a ride, and you should walk away from this person, send him no money and report him to the FBI at their Internet Crime Complaint Center.
If this is a real person and a real situation, then a Turkish contract will define precisely what would happen due to a failure to complete, and, of course, what happens would also depend on who breached that contract, which is arguable and can be litigated. The penalty for breaching would be a fine.
In general, however any company and contractor able to be successfully vetted to win a bid for a foreign contract would have credit and insurance which would cover unforeseen expenses and the contract itself should have indemnification provisions.