Discovered while testing MC-265218 and MC-261324. In creative mode and spectator mode, players promptly cease burning, leading one to anticipate their air supply would replenish. However, the air gauge remains static, neither decreasing nor increasing. Furthermore, transitioning into spectator mode causes the player to thaw out in powder snow. Nevertheless, if the switch to creative or spectator mode occurs while submerged, the air level does not regenerate. Whether this constitutes a feature request is debatable, but I perceive it as an inconsistency warranting consideration by Mojang.

steps to reproduce

1. /scoreboard objectives add playerAir air

2. Place a repeating command block and power it
3. Put the following command into the repeating command block:

   execute as @a run title @s actionbar {"score":{"name":"@s","objective":"playerAir"}}

4. Enter underwater while in survival or adventure mode
5. Switch to creative or spectator mode

Observed: Upon entering creative or spectator mode, your Air does not replenish. Additionally, returning to survival mode does not restore your Air, allowing for the issue to be reproduced without commands.
Expected: Your Air would refill when in creative mode.