Formula 1 title rivals and McLaren team-mates Lando Norris and Oscar Piastri face disqualification from the Las Vegas Grand Prix after a skid wear problem was recorded during post-race technical inspections.
Norris finished second with Piastri fourth in a race won by championship outsider Max Verstappen.
Both have now been referred to the stewards after the measured thickness of the rearmost skid on both McLarens was less than 9mm, the minimum thickness required by the technical regulations.
A technical infringement is usually a black-and-white matter so both drivers could be excluded. McLaren was called in to see the stewards at 11.45pm local time.
Standings right now
1 Norris 408
2 Piastri 378 (+30)
3 Verstappen 366 (+42)
Standings if McLarens excluded
1 Norris 390
2 Piastri 366 (+24)
3 Verstappen 366 (+24)
This would blow the championship fight wide open and let Verstappen make massive inroads on both, especially Norris.
It would slash Norris’s lead to 24 points ahead of both Piastri and Verstappen. Finishing second in Vegas had been set to extend Norris’s lead to 30 points over Piastri and 42 over Verstappen.
There are 58 points on offer across two rounds remaining, the Qatar Grand Prix - which includes a sprint race - and the finale in Abu Dhabi.
There was already uncertainty around the result, particularly for Norris, before the reported technical infringement - but it was assumed to be for different reasons.
Norris had taken drastic action to lift and coast aggressively at the end of the race, losing around 14 seconds to Verstappen in the final four laps.
This appeared to be an attempt to save enough fuel to finish the race, and provide a sample to the FIA for inspection afterwards, especially as one of the radio messages to Norris said “the fuel looks OK now”.
Norris referenced "some issues with the car" afterwards and also said: "I am not sure how close it was, I don't know if the sensor was saying things it shouldn't have been, or we just used more than expected, or what it was.
"I don't know the full extent, I need to go and see the team and understand more, to be honest."
But this was part of an unexpansive post-race position adopted by McLaren, which avoided detailing the specifics of the problem.
And its communication to Norris during the race strongly implied its instructions were being driven by a fuel concern - when it may instead have been to try to protect the plank, as reducing speed at the end of the straights avoids the underneath of the floor smashing into the track surface as much.
The intrigue was escalated when the cars were held for longer than normal in parc ferme, which is the time when all legality checks are taking place.
McLaren team principal Andrea Stella was also seen in conversation with FIA F1 technical head Nikolas Tombazis in McLaren’s hospitality unit, and Tombazis was spotted in the McLaren garage, too.
It was therefore initially assumed that it related to a serious issue relating to the fuel in Norris’s car, before technical delegate Jo Bauer’s report revealed it was actually plank wear on both McLarens.
