Check out the story below. Two passengers were on the U.S. 'no-fly' list and a KLM flight was therefore denied overflight of U.S. territory. Note that neither the U.K. nor Saudia Arabia detained or arrested these individuals when they returned through the U.K. to Saudi Arabia. One doubts that either of these states would have hesitated if there had been any real evidence.
Expatica - Living in, moving to, or working in the Netherlands, plus Dutch news in English: "The two passengers who were on the US 'no-fly list' were not arrested at Schiphol and were flown via England back to Saudi Arabia, their land of origin, where they were not refused entry either. Neither British nor Dutch authorities decided to detain them."