Danilo Petrucci led a factory Ducati one-two by 0.217 seconds over late faller Andrea Dovizioso on the first day of the final MotoGP pre-season test of the year at Jerez.
Cold temperatures meant it would be two hours after the session was green-lit before any running was had, with the Suzuki of rookie Joan Mir the first to venture out at 1130 local time.
By midday, Marc Marquez had navigated his Honda to the top of the timesheets with a 1:39.481s, putting him close to seven tenths clear of KTM's Pol Espargaro.
Marquez would soon be dethroned by the Ducati pairing of Dovizioso and Petrucci, the latter moving ahead with a 1:39.244s, before the latter edged clear with a 1:39.127s at 1300 local time.
Five minutes later, the session was halted while the air fence at Turn 7 was replaced, after Mir popped it in a crash.
The Suzuki rider was taken to the medical centre for checks, but was unharmed in the crash and would return to action later in the day to complete 52 laps for the Japanese marque, who is testing a new engine and chassis.
Petrucci's lap stood for some time, though with just over three and a half hours to go, Alex Rins on the sister GSX-RR cut his lead down to just 0.048s.
Moments later, Jorge Lorenzo moved his Honda ahead of his Ducati replacement by 0.378s with a 1:38.749s. The Spaniard's reign was short, however, as former teammate Dovizioso re-established top spot with a brace of session-best laps, culminating in a 1:38.519s.
Marquez returned to top spot with three hours to go by just 0.002s, while Yamaha's Maverick Vinales seized the position away from him with a 1:38.376s with 70 minutes remaining as he continued his work on the M1's new engine.
Petrucci hit the front around 20 minutes later with a 1:37.968s, while Dovizioso suffered a small crash late on at Sito Pons as he put this time under threat.
With no further improvements in the closing stages, Petrucci remained fastest on his GP19 from Dovizioso despite his tumble, while LCR Honda's Takaaki Nakagami impressed in third ahead of Vinales.
Marquez, who trialled a new aero package, completed the top five on the first of the Honda's, with Petronas SRT's Franco Morbidelli sixth and just 0.691s off the pace as he continued to adjust to the Yamaha.
Lorenzo was shuffled back to seventh ahead of Pramac's Jack Miller, Michele Pirro's stand-in at the Ducati test team Alvaro Bautista and top rookie Mir, while Andrea Iannone was best of the Aprilia's 0.052s behind his Suzuki replacement on the best of the Aprilias in 11th.
Valentino Rossi suffered a technical issue on one of his works M1s and faded from the top 10 to 17th in the end, 1.5s off the pace, with Aprilia tester Bradley Smith and KTM's Johann Zarco shadowing the Italian.
Aprilia's Aleix Espargaro was absent due to illness, but hopes to ride on Thursday. Smith took his place, while Matteo Baiocco [24th] rode for the Noale marque's test team.
| Pos | Rider | Team | Time | Gap | Laps | |
| 1 | PETRUCCI, Danilo | Ducati Team | 1:37.968 | 44 / 53 | ||
| 2 | DOVIZIOSO, Andrea | Ducati Team | 1:38.185 | 0.217 | 53 / 53 | |
| 3 | NAKAGAMI, Takaaki | LCR Honda IDEMITSU | 1:38.348 | 0.380 | 57 / 67 | |
| 4 | VIÑALES, Maverick | Yamaha Factory Racing | 1:38.376 | 0.408 | 55 / 58 | |
| 5 | MARQUEZ, Marc | Repsol Honda Team | 1:38.517 | 0.549 | 28 / 50 | |
| 6 | MORBIDELLI, Franco | Petronas Yamaha SRT | 1:38.659 | 0.691 | 53 / 69 | |
| 7 | LORENZO, Jorge | Repsol Honda Team | 1:38.749 | 0.781 | 31 / 56 | |
| 8 | MILLER, Jack | Alma Pramac Racing | 1:38.816 | 0.848 | 61 / 72 | |
| 9 | BAUTISTA, Alvaro | Ducati Test Team | 1:38.830 | 0.862 | 36 / 64 | |
| 10 | MIR, Joan | Team SUZUKI ECSTAR | 1:38.956 | 0.988 | 52 / 52 | |
| 11 | IANNONE, Andrea | Aprilia Racing Team Gresini | 1:39.008 | 1.040 | 20 / 24 | |
| 12 | RABAT, Tito | Reale Avintia Racing | 1:39.097 | 1.129 | 49 / 53 | |
| 13 | RINS, Alex | Team SUZUKI ECSTAR | 1:39.150 | 1.182 | 29 / 87 | |
| 14 | BAGNAIA, Francesco | Alma Pramac Racing | 1:39.157 | 1.189 | 50 / 51 | |
| 15 | ESPARGARO, Pol | Red Bull KTM Factory Racing | 1:39.241 | 1.273 | 48 / 58 | |
| 16 | QUARTARARO, Fabio | Petronas Yamaha SRT | 1:39.414 | 1.446 | 59 / 59 | |
| 17 | ROSSI, Valentino | Yamaha Factory Racing | 1:39.564 | 1.596 | 28 / 50 | |
| 18 | SMITH, Bradley | Aprilia Racing Test Team | 1:40.174 | 2.206 | 64 / 69 | |
| 19 | ZARCO, Johann | Red Bull KTM Factory Racing | 1:40.192 | 2.224 | 45 / 56 | |
| 20 | ABRAHAM, Karel | Reale Avintia Racing | 1:40.438 | 2.470 | 29 / 43 | |
| 21 | SYAHRIN, Hafizh | KTM Tech 3 Racing | 1:40.630 | 2.662 | 38 / 51 | |
| 22 | GUINTOLI, Sylvain | SUZUKI Test Team | 1:40.743 | 2.775 | 31 / 48 | |
| 23 | OLIVEIRA, Miguel | KTM Tech 3 Racing | 1:41.699 | 3.731 | 57 / 61 | |
| 24 | BAIOCCO, Matteo | Aprilia Racing Team Gresini | 1:42.766 | 4.798 | 44 / 49 |
