Daly took part in last year’s Indy 500 for Dale Coyne Racing, only narrowly making the race after James Hinchcliffe and Pippa Mann were eliminated on bump day.
The former GP2 driver has completed just two full IndyCar seasons since his return to America following his spell competing in European junior single seaters and made occasional starts in the series for Harding Racing last year.
Daly’s 2019 drive at the Indy 500 will be his sixth entry to the race and his second with key sponsor US Air Force, which has now joined the Andretti fold.
“I couldn’t be prouder to represent the Air Force for a second consecutive year at the Indianapolis 500,” said Daly.
“I would not be here without the effort from everyone at Andretti Autosport to make sure this programme is structured for success.
“It means a lot to see the commitment that the Air Force has shown in me, and the chance to have a shot at winning the biggest race in the world.
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“To be teamed with some of my best friends at undoubtedly one of the best teams on the grid is going to be a lot of fun!
“I’ve never had the chance to be on a team with multiple 500 winners so I am beyond excited to learn from them and ready to get to work.”
Andretti has traditionally run extra entries for the Indy 500 beyond its four seats for regular drivers Alexander Rossi, Ryan Hunter-Reay, Marco Andretti, and Zach Veach.
Last year it ran additional cars for Carlos Munoz and Stefan Wilson.