Lundgaard, who scored his first podium finish in the Indianapolis Motor Speedway’s second race on the road course last month, went on to score his highest grid slot in Nashville, and only slipped out of podium contention in the closing laps.
He currently leads David Malukas of Dale Coyne Racing by 41 points in the Rookie of the Year battle.
Lundgaard made his debut with the Honda-powered team co-owned by Bobby Rahal, David Letterman and Mike Lanigan as a one-off last summer, qualifying fourth at the IMS road course.
The 20-year-old Dane stated: “I have to say a big thanks to Bobby, David and Mike for giving me this opportunity to extend my time with the team. We’ve had some good results lately and I’m sure this has also helped their decision.
“First of all, I’m just happy and super excited that they gave me this opportunity.
"A year ago at the Grand Prix, we qualified well and they decided that they wanted me for a full season and we made the most of the opportunity so far. I’m sure there are times when we could have performed better but now we have the opportunity to continue this progress.
“We’ve been to a lot of tracks so far and have come back to some and finished on the podium, which I hope to continue.
"Qualifying third in Nashville was a big milestone for me. Making the Fast Six – and not being at the end of the Fast Six but actually having a shot at competing for the pole – was a great experience for me.
“We didn’t quite finish where we wanted but it was good to have that experience and now everyone is making the most of it.
"I’m happy for everyone at the team, my family and the sponsors and investors, everyone that has made this possible. I’m looking forward to continuing to build momentum.”
Three-time Indy car champion and 1986 Indy 500 winner Rahal said: “I am so pleased with Christian’s progress with the team and within the series. He has shown that he can be a force to be reckoned with in these races.
“He works well within the team, and we are pleased that we are continuing for the next several years because I believe he will continue to improve and be a potential winner in the very near future.”
Lanigan concurred, adding: “Christian has done a great job acclimatising to the variety of challenges and new experiences this season.
"His approach and professionalism continues to impress us and his performance, especially in the second half of the season, speaks volumes about his potential.
"We are very happy to have him as part of the team for the years ahead.”
