Honda is investigating the cause behind a double failure of its exhaust energy recovery system on Sunday. Yusuke Hasegawa promised that "countermeasures" would be in place in time for the next race in Mexico.
Even before the start of the United Stated Grand Prix, Stoffel Vandoorne had been sent to the back of the grid. McLaren had detected issues with his car's MGU-H in the morning, and the change incurred a hefty penalty.
In the race itself, Fernando Alonso's MGU-H failed 24 laps into the race. He had been running in seventh place and was set to win some crucial points for the team before his retirement.
"Today really was a missed opportunity," Alonso said after the race. "On the straight I lost power. I felt some vibrations in the engine and some really weird things were going on.
"It's such a pity. In the last few races we have lost so many points. Possibly 15 or 20, which probably could have helped our position in the championship for myself and also the team. It's painful."
"[It] was an incredibly frustrating day for everybody in the team," admitted Hasegawa, Honda's F1 project lead. "Reliability issues across both cars cost us a top ten finish.
"We detected an issue with Stoffel's MGU-H and made the decision to switch his power unit [in the morning]," he explained.
"Fernando started today from eighth on the grid and was up into seventh at the start. He maintained his position and kept his rivals behind him, until his race came to a premature end because of an MGU-H issue.
"It's very disappointing that we faced more issues with our power unit," Hasegawa said. "Particularly because the reliability has been relatively stable in recent races."
Alonso’s early exit in Austin was the team's first mechanical DNF since the Italian Grand Prix in July.
"We will immediately investigate the issue with the Sakura team," he pledged. "[Honda] will work towards a countermeasure for Mexico next weekend."
McLaren's racing director Eric Boullier was unimpressed by the latest misfortune to befall the team.
"Today was another race where we witnessed the talent of both our drivers but came home bitterly disappointed and with little to show for it," he said.
"Fernando started brilliantly," he continued. He had the capability to secure seventh or even sixth place and score valuable points for the team.
"But he was denied due to an MGU-H issue, which compounded the problems we've faced all weekend, albeit on the other car.
"It's a huge shame that these issues robbed us of a strong result at one of the few tracks left this season where we were hopeful of a more positive outcome.
"The problem encountered on Fernando's car means that Mexico will be another tough race for us, but we'll keep on fighting."