Lewis Hamilton led a Mercedes one-two from George Russell in first practice as Formula 1 returned to The Strip at the Las Vegas Grand Prix.
The Silver Arrows took advantage of fitting the softest - and fastest - tyre compound in the closing stages of the session on a rapidly improving surface under the city's stunning lights to finish well clear of the rest of the field.
Hamilton's time of 1:35.001s put him almost 0.4s clear of Russell, while McLaren's Lando Norris and Ferrari's Charles Leclerc were marginally either side of a second back from the seven-time world champion in third and fourth, respectively.
Max Verstappen, who can seal his fourth successive drivers' title in Sunday's race, was also just over a second back from Hamilton in fifth.
Verstappen could win the world championship with two races to spare by simply finishing ahead of Norris on Sunday, while the Dutchman would also be crowned if he avoided losing three points or more to the McLaren driver.
Carlos Sainz was sixth for Ferrari, who many considered the favourites coming into the weekend due to both their strong performance on F1's return to Las Vegas last year, and strong run of recent form.
Ferrari are attempting to close a 36-point deficit to Constructors' Championship leaders McLaren, with Red Bull a further 13 points adrift.
Slippery start fails to paint clear Vegas vista
The extraordinary nature of the event, which sees Las Vegas' famous Strip shut down to allow F1 to take over for three November nights, results in the circuit being far more dirty than the drivers are used to.
The opening session began with a chorus of complaints over radio, with Verstappen comparing the conditions to "driving on ice".
That was despite Red Bull being the only team to send their drivers out on soft tyres to start with, as the majority of the field began on mediums.
The times gradually improved as the circuit was rubbered in, but the real action began when Ferrari switched to softs with about 20 minutes remaining and shot to the top of the timesheet.
Norris improved the benchmark moments later, but it was Mercedes, who had also shown strong pace on the medium compound, who waited until the closing stages.
Russell and Hamilton both did two flying laps, with each one setting a new fastest lap. That meant Hamilton, who was behind his team-mate on track, had the chance to have the final word, but made it an impressive one by going substantially faster.
Mercedes, whose form has fallen away since the sport's summer break, must now avoid a repeat of several other occasions this season when they have impressed in early practice sessions before dropping off the pace later in the weekend.
There was nothing like the drama of last year's first practice when a loose drain cover caused a lengthy delay, but minor changes - in the form of some fresh paint - may be required to help the drivers stay within the lines of the pit lane entry.
Williams duo Alex Albon and Franco Colapinto were both given warnings for failing to remain within the faded white entry line, while Russell came onto team radio to express concern on the matter.
Sky Sports F1's live Las Vegas GP schedule
Friday November 22
5.45am: Las Vegas GP Practice Two
7.15am: The F1 Show*
Saturday November 23
2.15am: Las Vegas GP Practice Three*
5am: Las Vegas GP Qualifying build-up*
6am: LAS VEGAS GRAND PRIX QUALIFYING*
8am: Ted's Qualifying Notebook*
Sunday November 24
4.30am: Grand Prix Sunday: Las Vegas GP build-up*
6am: THE LAS VEGAS GRAND PRIX*
8am: Chequered Flag: Las Vegas GP reaction*
9am: Ted's Notebook*
*also live on Sky Sports Main Event
Formula 1 returns with the Las Vegas Grand Prix this weekend, live on Sky Sports F1 where Max Verstappen could seal the championship. Stream the final three F1 races and more with a NOW Sports Month Membership - No contract, cancel anytime
