Ferrari made a strong start to the first day of Formula One testing, on Monday, with four-times world champion Sebastian Vettel top of the timesheets at lunchtime with 72 laps completed.
The Italian team won six of the 21 races last year, finishing overall runners-up, and are hoping the new SF90 car can end Mercedes's five-year stranglehold on both championships.
Vettel's fastest lap of one minute 18.161 seconds, on a sunny morning at Barcelona's Circuit de Catalunya, was already quicker than anything set during the weather-hit first four-day test of 2018.
The German was also nearly two seconds faster than the best of the rest.
Racing Point's Mexican Sergio Perez was next on the timesheets, with a 1.19.944, on a day when mileage mattered more than outright speed as teams get to grips with their new cars for the first time and focus on getting in plenty of laps.
Reigning champions Mercedes, with Valtteri Bottas first behind the wheel of the silver W10, completed the second most laps -- three fewer than Ferrari -- with Renault's Nico Hulkenberg doing 65.
Five-times world champion Lewis Hamilton will take over from Bottas, who was third fastest, in the afternoon.
Former champions McLaren also made a solid start with Spaniard Carlos Sainz, stepping into the shoes of departed compatriot Fernando Alonso, completing 56 laps with the sixth fastest time.
Red Bull, now powered by Honda after their split from Renault, managed 52 laps with Dutch driver Max Verstappen in action.
Alfa Romeo, the renamed former Sauber team, had 2007 champion Kimi Raikkonen in new overalls after leaving Ferrari and completing 46 laps after an early trip into the gravel that brought out the first red flag of 2019.
The Finn was fourth fastest at the lunch break.
Russian Daniil Kvyat was slowest in the Honda-powered Toro Rosso but did more laps than Romain Grosjean, who did only 18 for Haas, while Perez took Racing Point's tally to 20.
Only nine of the 10 teams appeared on track, with struggling Williams failing to get their car ready on time and not expecting to test until Wednesday at the earliest.
Williams suffer further delay to F1 testing
Williams are set to miss at least the first two days of Formula One's opening pre-season test after failing to get their new car ready in time.
The former world champions said on Monday, as cars from the other nine teams lapped Barcelona's Circuit de Catalunya, that they were unlikely to get on track until the third day.
"It is looking more likely than not that we will now not be in a position to run on track until Wednesday at the earliest," said deputy principal Claire Williams in a statement.
"This is obviously extremely disappointing, but it is unfortunately the situation we are in. We will be getting the FW42 on track as soon as we are able."
Williams finished last overall in 2018 with a car that scored a mere seven points from 21 races despite having the same engine as champions Mercedes.
The poor performance has meant less prize money for the team while the loss of Martini, replaced as title sponsors by telecom company ROKiT, and departure of other backers has also had financial implications.
Williams said on Sunday that they would be sitting out Monday's session.
"We have had an incredibly busy winter at Grove getting the FW42 prepared for the season ahead and, despite everyone’s best efforts, we need some more time before it will be ready to run," Claire Williams said then.
Williams have a changed line-up for the new season starting in Australia on March 17, with British rookie and Formula Two champion George Russell partnering Poland's Robert Kubica, who has returned from a near-fatal rally accident in 2011.
