A grid penalty has soured what looked set to be a promising day for McLaren and for Jenson Button in particular after the former world champion finished second in the timings in Free Practice 1 on Friday morning.

Button was one of the cars out on track in the first 15 minutes of the delayed FP1 session just before the practice was red flagged as a result of a problem with the medical helicopter.

While returning to pit lane, Button overtook another car - something strictly forbidden under red flag conditions. The incident was reported to the race stewards, who duly handed down a three-place penalty after using video evidence to confirm the de facto breach of Appendix H, Article 2.4.4.1 (b)(3) of the FIA International Sporting Code.

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The penalty is likely to ensure that Button starts Sunday's Grand Prix outside the top ten for the penultimate race of the season, and probably behind his current team mate Sergio Perez.

The reasons behind the lengthy delay with the medical helicopter and the need to red flag FP1 have been clarified, as it emerged that it wasn't simply a case of the 'copter being grounded away from the track.

Instead, it's transpired that the medical transport had to turn back after developing a problem with its radio communications antenna, causing it to lose contact with the air traffic control tower at the Circuit of the Americas.

The 'copter diverted to a local airport for the necessary repairs, but the delay forced race director Charlie Whiting to suspend race activity for the duration.