(Read More: United Airlines to Fly Denver-Tokyo Nonstop With Boeing 787)
The daily flight to Tokyo's Narita International Airport was originally scheduled to begin March 31, but was delayed because of the worldwide grounding of all Boeing 787s over concerns about the safety of its battery system.
United resumed flying the 787 domestically on March 20 after the Federal Aviation Administration approved a battery fix and lifted the grounding.
(Read More: United 787 Makes Uneventful Return to the Skies)
"This new nonstop service between Denver and Tokyo will build a new bridge between Colorado and all of Asia, strengthening our global connectivity and elevating the entire Denver area onto the international stage," said Michael B. Hancock, Denver's mayor, in a prepared statement. "We thank United Airlines for its partnership on this new frontier of opportunity and its commitment to the Denver market."
Seth Miller, a frequent traveler and loyalty program analyst from New York who authors the Wandering Aramean blog, booked his ticket months ago and was among the inaugural passengers.
"I am always looking for opportunities to have unique travel experiences and inaugurals are a good opportunity for that," Miller said. "So much of air travel has become boring, rote repetition; flights like this break that up and provide a refreshing change of pace."
Monday's flight was Miller's third onboard a 787 and he had absolutely no qualms about the jetliner's safety.