Travel expenses - flight invoice/order confirmation

Hello, Company Director goes for business trips and buys flight tickets on various internet platforms. Not every tickets platform issues an invoice in the name of the Company. Is it enough to have an email with flight order confirmation where is indicated Directors name, flight destination and the amount paid for flight ticket? Is it acceptable for Corporation tax purposes to treat such expenses as allowable? Many thanks for the replay.

Hi,
Any documentation that clearly confirms the information needed can be used, however if it is requested by HMRC you may need to explain what/why you are providing that kind of documentation. 
As for if this is an allowable expenses HMRC are unable to give tax planning advise it is, your responsibility to self-assess. 
You may want to look at CTM08000 - Corporation Tax: management expenses: for information on what is classed as allowable or not. 
Thank you.