Transfer this incident to a business environment.
You're a software provider and you have a contractual obligation to deliver a core business application to your customer at a specific time in a sunset scenario. (Old application HAS to be switched off then and then, new application HAS to be seamlessly introduced)
Together with the customer, you define the business (use) cases to be validated, develop a test plan with adequate time buffers and perform and document the tests.
At some point during the test plan, you determine that you're unable to complete all acceptance tests without jeopardising your delivery date. The reasons are irrelevant - external factors, poorly structured test plan, repeated testing in order to validate bug correction.
The fact is that you're left with some minor uncritical business cases to test, but in testing them, you're running the risk of not being able to compile the application in time for on-line release.
What do you do?
Press on regardless and risk a catastrophic commercial outcome if the final compilation doesn't work first time (with no second chance), or release the application in a stable state and continue testing off-line?
It comes down to risk assessment - is the risk we're engaging in commensurate with the benefits?
In this case: was the acceptance test required to be concluded with the touch and go at Perpignan or could the low speed tests have been performed enroute to EDDF?