(Reuters) - Max Verstappen lapped fastest for Red Bull as Lewis Hamilton and Formula One champions Mercedes endured a surprisingly difficult first day of pre-season testing in sandstorm-hit Bahrain on Friday.
Verstappen completed a whopping 139 laps while seven times champion Hamilton, who took over from team mate Valtteri Bottas after the lunch break, managed a mere 42 and was 2.2 seconds off the pace.
Bottas was able to do only six laps in the first session due to a gearbox problem, with the wind and sand whipping up after lunch.
The combined tally of laps by the Mercedes pair was the lowest of all teams and Hamilton seemed to be struggling for grip on the sandy surface, while also having to deal with a wobbly wing mirror and complaining about the pedals.
"It wasn't a good start," said Mercedes team boss Toto Wolff, adding that the gearbox issue "came out of nowhere".
"If we have a smoother ride from here onwards then I think we can recover, if we have more stumbling blocks then with three days there's not a lot we can do."
The Sakhir circuit is hosting three days of testing, half the amount the 10 teams had available last year at Barcelona's Circuit de Catalunya, before the opening race in the Gulf kingdom on March 28.
Mercedes are chasing an unprecedented eighth successive title double this year with Hamilton aiming for his record eighth championship.
"The second session wasn't without its challenges, but we exist to find solutions to the problems we're faced with," said Hamilton.
"I've never seen a sandstorm come through here before in all the years that I've driven at this circuit. The sand was moving like rain would move."
Verstappen's best time was one minute 30.674 seconds on the C3 tyre compound.
"We don’t need to talk about pace yet and it isn’t really a discussion until we get to Q3 (final qualifying) at the first race weekend -- it’s only then you see the real pace in all the cars," said Verstappen.
"The main thing is that the car felt nice to drive, so it’s a positive start."
McLaren's Daniel Ricciardo topped the morning timesheets in 1:32.203, completing 45 laps in a car that has switched from Renault to Mercedes power, with AlphaTauri's Pierre Gasly second and getting 74 laps done.
Ferrari's Charles Leclerc brought out red flags 10 minutes before the lunchtime break when his car stopped on track. He was fifth fastest then but ended the day 11th.
New team mate Carlos Sainz took over for the second session and was fifth overall.
Haas had hydraulic problems, with rookie Mick Schumacher managing only 15 laps and ninth fastest in the morning but Russian Nikita Mazepin getting in 70 laps later.
With all launches conducted remotely and some teams publishing only edited digital images, the opening session saw the cars finally running in full view of the cameras in their new liveries.
The session was a first for Alpine, the renamed Renault team, and marked Aston Martin's return as a constructor for the first time since 1960.
The main focus of testing is to confirm reliability and add performance, although with many parts carried over from 2020 the emphasis this year is more on the latter.
(Reporting by Alan Baldwin in London, editing by Timothy Heritage/Toby Davis/Ken Ferris)