Grand Canyon, by the cube
Three airports get you to Grand Canyon: Flagstaff (FLG), Grand Canyon National Park (GCN), and Las Vegas (LAS). Each has trade-offs around fare, frequency, and ground time.
FLG — Flagstaff Pulliam
FLG is the closest scheduled-airport to the South Rim, 90 minutes by car. Regional-jet service from PHX and DFW is operated by code-share partners on behalf of a larger carrier; the IATA carrier codes for those flights are typically OO and YV. Fares are typically $138-$200 round-trip from PHX. Winter weather cancellations are common between December and March; build a buffer day.
GCN — Grand Canyon National Park
GCN sits in Tusayan, immediately south of the South Rim entrance. Scheduled service is limited to small Part 121 operators (Contour, Boutique Air seasonal). Most GCN traffic is helicopter and small-plane tour flights from Las Vegas. For travelers without a rental, GCN plus a Tusayan shuttle gets you to the rim in 30 minutes.
LAS — Las Vegas (day-trip)
LAS is the cheapest gateway and a feasible day-trip from PHX. PHX-LAS is under $90 round-trip from every carrier; the canyon is a 4.5-hour drive from LAS via I-40 and US-180. For a single-day round-trip, take a 6 AM PHX-LAS, rent a car at LAS, and return on a 10 PM LAS-PHX. It's a long day but it works.
Ground-transport notes
From FLG, Arizona Shuttle (now Groome) runs a daily fixed-route service to Tusayan and the rim. From GCN, the National Park Service runs free shuttles around the South Rim and to popular trailheads. From LAS, no scheduled bus service goes to the rim; a rental car is required.