McLaren began planning an entry for him in the 2019 IndyCar Series in August 2018 and would be supported by the series. Alonso tested a 2018-specification Andretti Autosport-entered Dallara DW12-Honda at the Barber Motorsports Park on 5 September. McLaren opted to enter just the 2019 Indianapolis 500 due to its focus on Formula One and collaborated with Carlin Motorsport in a logistical and technical partnership and signed an engine supply deal with Chevrolet. Alonso ventured to the McLaren Technology Centre in early March 2019 for a seat fitting to become comfortable in the No. 66 Dallara IR18-Chevrolet and its brake pedal was shifted away from his feet since it is used less in IndyCar than in Formula One. Andy Brown was Alonso's race engineer and his chief mechanic was Liam Dance. Alonso did not qualify after Juncos Racing's Kyle Kaiser demoted him to 34th. Reasons included a dismantled spare car needed to assembled and flown from Carlin's factory after Alonso crashed in practice. An error converting inches to the American metric system caused his car to scrape along the tarmac surface and incorrect gear ratios slowed him.