Sunday's race will be Hamilton's last for Mercedes before joining Ferrari as Carlos Sainz's replacement.
Alpine's Pierre Gasly was fifth fastest, with new Australian teammate Jack Doohan 19th in preparing for his first race as replacement for Esteban Ocon.
Nico Hulkenberg was sixth for Haas with Williams' Franco Colapinto seventh but facing a five place grid drop for gearbox changes. Colapinto's teammate Alex Albon will have a similar penalty.
In a Formula One first, two brothers took to the track for the same team in the same session — Leclerc being joined by younger brother Arthur (18th) in the other Ferrari usually driven by Spaniard Sainz.
Six of the 10 teams had a young driver at the wheel of one of their cars, fulfilling an obligation to give them track time.
Japan's Ryo Hirakawa replaced Oscar Piastri at McLaren, Isack Hadjar drove quadruple champion Max Verstappen's Red Bull and Felipe Drugovich was in Lance Stroll's Aston Martin.
Ayumu Iwasa stood in for fellow-Japanese Yuki Tsunoda at RB and Luke Browning for Alex Albon at Williams.
Leclerc penalty a major setback for Ferrari’s title hopes
Image: Clive Mason/Getty Images
Ferrari suffered a severe setback to their hopes of winning the Formula One constructors' title for the first time since 2008 when Charles Leclerc was handed a 10-place grid penalty on Friday.
Leclerc set the fastest lap in the first practice session at Yas Marina but Ferrari then revealed they had changed his car's battery, triggering an automatic penalty for a breach of the regulations.
The governing FIA confirmed in a technical report Leclerc was now using his third energy store for the season, one more than allowed.
Ferrari are 21 points behind leaders McLaren, last champions in 1998, with 44 still to be won on Sunday and third-placed Red Bull out of the running.
Leclerc lapped with a best time of 1:24.321 seconds, with McLaren's Lando Norris 0.221 slower and the Mercedes pair of seven-time world champion Lewis Hamilton and George Russell third and fourth.
Hamilton was being investigated by stewards for allegedly impeding Norris, however.
O brother, how fast art thou? Leclerc and Leclerc in F1 practice first at Ferrari
Sunday's race will be Hamilton's last for Mercedes before joining Ferrari as Carlos Sainz's replacement.
Alpine's Pierre Gasly was fifth fastest, with new Australian teammate Jack Doohan 19th in preparing for his first race as replacement for Esteban Ocon.
Nico Hulkenberg was sixth for Haas with Williams' Franco Colapinto seventh but facing a five place grid drop for gearbox changes. Colapinto's teammate Alex Albon will have a similar penalty.
In a Formula One first, two brothers took to the track for the same team in the same session — Leclerc being joined by younger brother Arthur (18th) in the other Ferrari usually driven by Spaniard Sainz.
Six of the 10 teams had a young driver at the wheel of one of their cars, fulfilling an obligation to give them track time.
Japan's Ryo Hirakawa replaced Oscar Piastri at McLaren, Isack Hadjar drove quadruple champion Max Verstappen's Red Bull and Felipe Drugovich was in Lance Stroll's Aston Martin.
Ayumu Iwasa stood in for fellow-Japanese Yuki Tsunoda at RB and Luke Browning for Alex Albon at Williams.
READ MORE:
Hamilton ‘massively underestimated’ how hard his Mercedes farewell would be
Constructors' title would be perfect farewell to Ferrari, says Sainz
Verstappen sad but proud about Dutch GP departure after 2026
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