Austin MotoGP: Marc Marquez leads drying practice for Honda

Friday's second practice session started slowly as the track remained damp from the earlier rain, but became frantically busy in the closing stages once it was possible to use slicks.

With forecasts suggesting practice three on Saturday will be wet, Friday afternoon's session became the critical one for earning a pass straight through to Q2.

Amid incessant changes of position as the track improved with every lap, Espargaro brothers Pol and Aleix led the way for a while before Marquez, Crutchlow and Iannone all took turns on top.

In the end it was world champion Marquez - who had been the last rider to try slicks - who put his Honda back into first place in the final minute with a 2m04.835s.

That pushed LCR man Crutchlow and factory Ducati rider Iannone back to second and third, both three tenths down.

Aleix Espargaro held on to fourth for Suzuki, ahead of Qatar Grand Prix lead rivals Andrea Dovizioso and Valentino Rossi.

The latter's team-mate Jorge Lorenzo was bumped out of the top 10 by an improving Stefan Bradl in the final moments, meaning he will have to go into Q1 unless he can improve his time in Saturday practice.

Bradley Smith clung on to a guaranteed Q2 spot in 10th place despite crashing his Tech 3 Yamaha at the first corner late on.

Avintia Ducati rider Hector Barbera also fell on his final lap of the day.

PRACTICE TWO RESULTS: