Ex-MotoGP racer Iannone will make his return to racing action in 2024 as his four-year doping ban expires after signing to join satellite Ducati squad Go Eleven next season.
Sampling the Ducati V4 R Panigale at Jerez this week, the Italian rider was a low-key 11th-fastest on the opening day of the test on Tuesday, which was curtailed by bad weather.
But taking advantage of improved conditions on Wednesday afternoon, Iannone turned heads as he set the fifth-fastest time of the day, lapping within a second of pacesetter Remy Gardner.
“It was really fun, I enjoyed today a lot," Iannone told the official WSBK website after completing 69 laps on Wednesday. "My feeling with the bike improved exit by exit and run by run.
"It’s really interesting because I’m a little bit surprised about the result, also the feeling with the tyre and everything. We have a lot of work in front of us, but we start from a really good point.
“We have really big ambitions. I want to come back, but I want to try to come back at a high level. I want to achieve these results and I want to try to arrive at the top.
"In any case, I know it’s really difficult because the level is really high. Everybody is close but, I think, for us and the first test, it’s difficult to achieve a little bit more.
"The bike impressed me on the positive side, and also the tyres. They’re friendly. You felt where the limits of the tyres are and the bike and I think this is a good point.”
For the second day in succession, GRT Yamaha rider Gardner topped the timesheets as he set a best lap of 1m38.448s to go a little under three tenths up on Nicolo Bulega on the works Ducati.
Jonathan Rea continued his adaptation to the Yamaha he will race next year with the third-fastest time, 0.731s off the pace, but marginally faster than former team-mate Alex Lowes on the Kawasaki.
Alvaro Bautista meanwhile struggled for outright pace as he spent time experimenting with the extra weight he will be forced to carry on his works Ducati next year as a result of new rules concerning combined minimum weight for rider and motorcycle.
The two-time champion was seventh-fastest, just over 1.5s off the pace, behind Michael Ruben Rinaldi on the satellite Motocorsa Ducati.
Axel Bassani found himself nearly three seconds off the pace and 12th of the 13 riders present as he continued his adaptation to the Kawasaki.
Further testing will be held at Jerez on November 22-23.
Jerez testing times (Wednesday):
1. Remy Gardner (GRT Yamaha) - 1m38.448s (61 laps)
2. Nicolo Bulega (Ducati) +0.278s (52)
3. Jonathan Rea (Yamaha) +0.731s (68)
4. Alex Lowes (Kawasaki) +0.763s (68)
5. Andrea Iannone (Go Eleven Ducati) +0.887s (70)
6. Michael Ruben Rinaldi (Motocorsa Ducati) +1.359s (69)
7. Alvaro Bautista (Ducati) +1.514s (58)
8. Bradley Ray (GMT94 Yamaha) +1.559s (59)
9. Dominique Aegerter (GRT Yamaha) +1.655s (67)
10. Scott Redding (Bonovo BMW) +1.843s (47)
11. Garrett Gerloff (Bonovo BMW) +1.886s (66)
12. Axel Bassani (Kawasaki) +2.898s (54)
13. Tarran Mackenzie (MIE Honda) +3.662s (39)
