Championship leader Lando Norris was fastest in a second practice session at the Las Vegas Grand Prix interrupted and then curtailed by a loose manhole cover.
The McLaren driver was 0.029 seconds ahead of Mercedes’ Kimi Antonelli, with Ferrari’s Charles Leclerc third, 0.161secs off the pace.
But the interruptions to the session meant a number of top drivers did not get runs on the soft tyre during the session, including Norris’ team-mate and title rival Oscar Piastri, Red Bull’s Max Verstappen and Ferrari’s Lewis Hamilton.
The manhole cover will likely mean a long night for race officials.
The problem emerged at Turn 17, the final corner, about 20 minutes before the end of the session.