Cool aviation pics: Hello Kitty jets; United, Frontier, Delta and more

A Frontier Airbus A321 passes under the landmark pedestrian bridge at Denver International Airport on May 7, 2017.

A passenger watches a United Airlines Airbus A320 pull into a gate at Denver International Airport on May 7, 2017.

Alaska Airline's veterans-themed Boeing 737 passes in front of Mt. Rainier before landing at Seattle Tacoma International Airport in May 2017.

United Airlines planes at Denver International Airport on May 7, 2017.

A Frontier Airbus A320 taxies out for departure from Denver International Airport on May 7, 2017.

A United Express CRJ regional lands at Denver International Airport on May 7, 2017.

An Alaska Airlines Boeing 737 taxies to the gate as a beautiful orange glow fills the sky at Seattle Tacoma International Airport in May 2017.

A United Express Embraer E170 teters during a crosswind landing at Denver International Airport on May 7, 2017.

A Delta Air Lines MD-90 taxies into the gate at Denver International Airport on May 7, 2017.

Condor's retro-painted Boeing 767-300 lifts off from Seattle-Tacoma International Airport for Frankfurt, Germany, on May 18, 2017.

Icelandair's unique northern lights-themed Boeing 757 arrives at Denver International Airport on May 7, 2017.

A Frontier Airbus A320 is leaded for its next flight from Denver International Airport on May 7, 2017.

Check-in kiosks with Frontier stand ready for customers at Denver International Airport on May 7, 2017.

The nose gear of a British Airways Boeing 747 rolls up to the stop line at the gate at Denver International Airport on May 7, 2017.

A Frontier Airbus A320neo taxies past Denver International Airport's unique central terminal on May 7, 2017.

Seven-year old Xavier, left, and his brothers Dominic and Luke pose for a photo in front of a vintage airplane at the annual Paine Field Aviation Day in Everett, Wash., on May 20, 2017.

A Memorial Day cemetery service underway receives a flyover from Historic Flight Foundation's World War II-era B-25 bomber during a special Memorial Day flight on May 29, 2017.

A Delta Air Lines Boeing 737 is readied to be towed to a new gate for the night at Los Angeles International Airport on May 12, 2017.

A member of a tug team prepares the first Boeing 737-900 to be towed over to Delta's new Terminal 3 digs at Los Angeles International Airport on May 13, 2017, during a major relocation effort that saw 15 airlines shifting in five nights.

A worker polishes off a newly-installed sign at Terminal 3 at Los Angeles International Airport on May 13, 2017 during a major relocation effort that saw 15 airlines shifting in five nights.

A gentleman has fun taking a selfie with an arriving Air France Airbus A380 near Los Angeles International Airport on May 13, 2017.

An Alaska Airlines Embraer E170 operated by affiliate SkyWest lands at Seattle-Tacoma International Airport on May 18, 2017.

Passengers transit through Terminal A at Denver International Airport on May 7, 2017.

An Alaska Airlines Embraer E170 takes off over company metal at Seattle Tacoma International Airport in May 2017.

Boeing's widebody factory in Everett, Wash., stretches out across Paine Field on May 29, 2017 (as seen from a Historic Flight Foundation Beaver aircraft).

Pilot John Sessions with the Historic Flight Foundation lines up his vintage Beaver aircraft with runway 34L at Paine Field, near Everett, Wash., on May 29, 2017.

Runway 34 at Renton Municipal Airport fills the windscreen of a World War II-era B25 on approach to the small airport in May 2017.