The session started with track temperatures nearly hitting 50°C, a point which was reached and surpassed by FP3's halfway point, and Verstappen led the field out of the pits – an atypical run plan for Red Bull in final practice, as the team usually leaves the garage late in FP3 to focus solely on qualifying preparation runs.
But after missing essentially all of FP2 with gearbox and hydraulic problems, Red Bull needed to give its world champion time to get up to speed on the Miami circuit, which meant he headed out as soon the session began to pound around on the medium tyres.
His initial benchmark at the head of the pack was a 1m34.037s, which was beaten at the end of the opening five minutes of the final one-hour practice session by Leclerc's 1m32.250s on the soft tyres.
But Verstappen's as opening run continued, he duly retook the top spot with a 1m31.55s set with 10 minutes completed.
At this stage the session was interrupted when Ocon crashed heavily into the barriers inside the tight chicane, beneath the public road underpass at the end of the second sector.
In very similar circumstances to Carlos Sainz's FP2 crash on Friday, the Alpine driver lost control of the rear of his car as he exited the rapid left of Turn 13 and slammed hard into the barriers on the outside after spinning backwards and then sideways towards the wall.
The impact broke the left-front from Ocon's car and the session was suspended for 13 minutes while the wreckage was cleared.
When the action resumed, the majority of the field headed out immediately again as they looked to make up for even more lost time following the red flags that blighted both Friday practice sessions.
Both Verstappen and Leclerc returned to the fray on the same compounds they had started FP3, with the latter cutting his rivals advantage to 0.231s shortly after the restart while the Verstappen lapped a few seconds off his best pace so far.
While Ferrari's championship leader soon came in to prepare for a third run on the softs, Verstappen continued to gather data on the mediums – still putting in times that suggested he was carrying a considerable fuel to prepare for the race and at one stage sliding deep at the fast right-hand Turn 1 after catching an oversteer snap, then later getting visibly frustrated catching Sebastian Vettel going slowly out of the chicane.
As the final 20 minutes commenced, Leclerc started another soft-tyre flying run, which he ended up taking back to the top spot with a 1m30.981s – 0.3s quicker than Verstappen's previous best, albeit after losing 0.3s in the final sector.
After a slow cool-down lap nearly a minute off the pace, Leclerc went for another flier – setting a purple sector one before losing time in the middle segment and then clawing time back in the final third, but not enough to improve the top time as he ended up 0.053s slower than his personal best.
He then pitted and the attention switched back to Red Bull, with Sergio Perez, who had also been doing high-fuel running during the early stages and so languishing in 18th, shooting ahead of Leclerc with a 1m30.699s as the session's final 10 minutes began.
But he did not stay top of long, as Verstappen's purple sector one and personal best in the middle sector was enough to get him ahead of his teammate with a 1m30.649s, even though he was slower than his own best final third on the mediums.
That had Verstappen top by 0.050s over Perez, with Leclerc 0.332s behind in third, but after a trip through the pits Perez responded with purple sectors in the first and final thirds to move back ahead on a 1m30.304s just as the final five minutes arrived.
That was enough time for one final run for both Verstappen and Leclerc, with the Red Bull going first and heading Perez's best by 0.2s in the first sector.
But Verstappen clipped the inside kerbs at the chicane too hard and he speared towards the wall on the exit of the second apex, only just getting it stopped with four locked wheels and avoiding a costly accident.
As Verstappen was returning to the pits, Leclerc was beating Perez's sector one time by 0.4s, but he lost all his advantage by the finish line to wind up 0.194s adrift, even as his late improvement meant he moved ahead of Verstappen in the final standings.
Fernando Alonso finished fourth for Alpine ahead of Vettel, with Mick Schumacher's last-gasp gain getting him ahead of Sainz – also making up for lost time with high-fuel runs early in FP3 – to finish sixth for Haas.
Kevin Magnussen had an early spin exiting the now doubly resurfaced Turn 17 half hairpin at the end of back straight, but kept it out of the wall and eventually finished eighth ahead of Alex Albon, who's strong form for Williams continued.
Lando Norris, who at one stage just ahead of the final third nearly hit the wall running on the back straight as he caught a big oversteer snap on worn hard tyres, completed the top 10.
After its promising and pace-setting Friday, Mercedes was brought back to earth with many bumps, as George Russell and Lewis Hamilton were spotted porpoising badly on their final performance runs.
The best of these put Hamilton 15th, while FP2 leader Russell was down in 17th – the younger Briton reporting at one stage that his tyres were "nowhere" as he and Hamilton had lock-ups and slides that nearly had them off the road.
| Cla | Driver | Chassis | Engine | Laps | Time | Gap | |
|---|---|---|---|---|---|---|---|
| 1 |  Sergio Perez |  | Red Bull | Red Bull | 21 | 1'30.304 | |
| 2 |  Charles Leclerc |  | Ferrari | Ferrari | 23 | 1'30.498 | 0.194 |
| 3 |  Max Verstappen |  | Red Bull | Red Bull | 20 | 1'30.649 | 0.345 |
| 4 |  Fernando Alonso |  | Alpine | Renault | 18 | 1'31.036 | 0.732 |
| 5 |  Sebastian Vettel |  | Aston Martin | Mercedes | 24 | 1'31.049 | 0.745 |
| 6 | Mick Schumacher |  | Haas | Ferrari | 19 | 1'31.050 | 0.746 |
| 7 | Carlos Sainz |  | Ferrari | Ferrari | 24 | 1'31.172 | 0.868 |
| 8 |  Kevin Magnussen |  | Haas | Ferrari | 20 | 1'31.227 | 0.923 |
| 9 |  Alex Albon |  | Williams | Mercedes | 14 | 1'31.501 | 1.197 |
| 10 |  Lando Norris |  | McLaren | Mercedes | 18 | 1'31.594 | 1.290 |
| 11 |  Yuki Tsunoda |  | AlphaTauri | Red Bull | 24 | 1'31.659 | 1.355 |
| 12 |  Lance Stroll |  | Aston Martin | Mercedes | 22 | 1'31.665 | 1.361 |
| 13 |  Daniel Ricciardo |  | McLaren | Mercedes | 19 | 1'31.728 | 1.424 |
| 14 |  Valtteri Bottas |  | Alfa Romeo | Ferrari | 26 | 1'31.885 | 1.581 |
| 15 | Lewis Hamilton |  | Mercedes | Mercedes | 20 | 1'31.890 | 1.586 |
| 16 |  Pierre Gasly |  | AlphaTauri | Red Bull | 18 | 1'31.901 | 1.597 |
| 17 | George Russell |  | Mercedes | Mercedes | 19 | 1'31.924 | 1.620 |
| 18 |  Zhou Guanyu |  | Alfa Romeo | Ferrari | 16 | 1'32.051 | 1.747 |
| 19 | Nicholas Latifi |  | Williams | Mercedes | 16 | 1'32.376 | 2.072 |
| 20 | Esteban Ocon |  | Alpine | Renault | 3 | ||
| View full results | |||||||
