A US-bound plane carrying 240 passengers was turned around mid-flight for security reasons.
American Airlines flight 109 left for Boston on Monday, but two hours into the journey it turned back to Heathrow Airport in west London.
Scotland Yard said four people were being "spoken to" at Heathrow, but no-one had been arrested.
A spokesman for Boston's Logan Airport said one passenger's name matched a name on the "no-fly" list.
There were 240 passengers and 13 crew members on board the Boeing 777 aircraft, which was due to touch down in Boston at 1805 BST.
But it was back on the runway at Heathrow by about 1530 BST.
A Scotland Yard spokeswoman said four people were being spoken to under port and border controls - a section of the Terrorism Act under which a person can be questioned and detained for up to nine hours.
But she stressed they had not been arrested.
In a statement, American Airlines said the plane returned to Heathrow "due to a security issue that needed to be resolved in London".
It added: "American Airlines has cancelled the flight and is working to rebook passengers on alternative flights to Boston.
"American Airlines regrets the inconvenience caused to its customers."