Alaska Airlines Boeing 737 taxiing at Palm Springs International Airport.

An Alaska Airlines Boeing 737-900ER in a distinctive Boeing-branded livery taxis past the busy gates at Phoenix Sky Harbor, with the desert mountains beyond the terminal.

Delta Air Lines Boeing 737-900ER N897DN parked at a gate, seen through the terminal windows.

Alaska Airlines Boeing 737-900ER N617AS taxis past the airport’s elevated roadway, with its distinctive portrait tail and split-scimitar winglets visible.

United Airlines Boeing 737-900ER N75436 among several aircraft at the airport, with its blue engine and wing prominent in the foreground.

Taxiing at PHX.

Landing at PHX.

Spotted taxiing in

Landing at PHX.

Spotted during takeoff in Prague airport

Gate area at ORD.

Heading to the gate at ORD.

Just landed at ORD.

Taxiing at ORD.

Taxiing at ORD.

Travel Service Boeing 737-900ER (OK-TSI) at the gate, featuring blended winglets and high-density layout.

Ready for pushback at ORD.

Taxiing at ORD.

TSRA sitting at the gate.

Pushback at DEN.