Barcelona - Ferrari's Sebastian Vettel outgunned reigning world champion Lewis Hamilton to the fastest time as the 2016 Formula One season got underway with the first test in Barcelona on Monday.
The Italian giants are expected to pose an even stronger challenge to Hamilton's Mercedes this season after Vettel showed signs of a Ferrari revival by winning three races last year.
The four-time former world champion was nearly half a second faster than Hamilton in a time of 1min 24.939sec.
However, after dominating the sport for the past two seasons, Mercedes' reliability sent another warning shot to the rest of the paddock as Hamilton racked up a huge mileage of 155 laps - nearly twice as much as anyone else.
History also favours Hamilton and Mercedes. Ferrari posted the quickest time on day one of testing in each of the last two years, whilst Mercedes clocked up the laps before moving up a gear closer to the start of the season.
Seven more days of testing remain at the Circuit de Cataluyna track before racing gets underway for real at the Australian Grand Prix on March 20.
Red Bull and Williams showed early signs of what could be a battle for the best of the rest as Daniel Ricciardo edged out Valtteri Bottas to third fastest.
Mclaren-Honda made a significant improvement on their disastrous performances in testing last season which set up a hugely disappointing return season to the sport for the Japanese manufacturer.
Despite a few early teething problems which frustrated race director Eric Boullier, Jenson Button was able to log 82 laps, but the MP4-31 was still well down on pace nearly two seconds behind Vettel in fifth fastest.
Unsurprisingly, newcomers Haas, the first American owned team in Formula One for 30 years, Renault on their return as a constructor and Manor Racing struggled most, although the three combined for over 100 laps on an uncharacteristically trouble-free first day of the season.