ST. LOUIS, Missouri (CNN) -- Barack Obama's plane made an unscheduled landing in St. Louis Monday after "an emergency slide located in the tail cone of the plane deployed in flight," according to the airline that owns the chartered plane.
The plane landed safely.
Midwest Airlines released a statement saying that while "there was never an issue as to the safety of the flight, as a precautionary measure, we decided to divert the plane."
Obama told reporters after landing it was the first time he had had to land because of mechanical problems.
"Just thought we'd spice things up a little bit today," he joked, adding: "Anytime a pilot says that something's not working the way its supposed to, then, you know, you make sure you tighten your seat belt. Everything seemed under control, the pilots knew what they were doing." 
See where Obama landed »
En route from Chicago to a campaign appearance in Charlotte, North Carolina, the pilot detected a "control ability issue" in the "pitch" of the plane. He said there was no need to assume the "brace" position and that he had "full authority of the aircraft." 
Watch Obama explain why the plane was diverted »
Fire trucks were waiting to meet the aircraft when it landed at Lambert-St. Louis International Airport.
Obama delivered his speech by telephone from St. Louis to about 200 people in Charlotte. He later continued onto Atlanata, Georgia, for a fundraiser in a smaller airplane.
The National Transportation Safety Board is investigating the incident, it announced Monday afternoon
CNN's Alexander Marquardt and Richard Greene contributed to this report.
All About Barack Obama • Charlotte (North Carolina) • St. Louis
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