There is a version of the Great Barrier Reef you cannot see from a boat, and it is the version on every postcard: ribbon reefs stacked in parallel to the horizon, sand cays sitting in turquoise rings, the abrupt navy line where the continental shelf drops away. From the water you see coral. From 500 metres you see the structure.
A 30-minute fixed-wing flight from Cairns costs $143, which makes it cheaper than every full-day boat on this site and only slightly more than a half-day snorkel. That surprises people, and it changes how the flight should be thought about: not as an alternative to a reef trip, but as an hour bolted onto a day you were having anyway.
The options split three ways. Fixed-wing scenic flights are the cheapest and cover the most ground — 140 kilometres of outer barrier in half an hour, everyone at a window, commentary through a headset. Helicopter flights cost more ($349 for 30 minutes from Cairns or Port Douglas) and fly lower and slower, which suits photography. Boat-and-flight combinations fly you out and cruise you back, or add ten minutes of helicopter time to a platform day — Quicksilver and the Cairns pontoon operators both sell that.
Two practical limits. Fixed-wing scenic flights here are not suitable for passengers over 115 kg, and everyone must be able to step into the aircraft unassisted. And flights are genuinely weather-dependent in a way boats are not: a marginal day means the flight is cancelled outright, rescheduled or refunded in full, rather than run in poor conditions.
If you have one day and cannot decide, take the boat. If you have a spare morning before an afternoon flight home — and cannot dive, because of the 24-hour rule — this is the best hour on the coast.