Yes. They use left/right. Port/starboard is useful when you have a crew of people running around doing jobs aboard a three-dimensional ship. Pilots are never more than two people sitting in fixed seats facing forwards. It is a much more linear environment than a ship.

More linear does make sense. "Full astern" is a thing for ships but not planes.

But it makes me wonder about helicopter pilots. Do they say left and right?

Yes.

Yes, pilots say left/right, although it is more common to use clock positions for that.

For example "traffic 3 o'clock" means there is someone on you right.

Port/starboard is not used in aviation and I don't know of any equivalent besides left/right.

> Port/starboard is not used in aviation

Some things seem to have been carried over though - you still almost always board an aircraft from the port side, don't you?

And port/left is still a red light, and starboard/right is still a green light, on aircraft.

A good way to remember all this is 'port is red and is passed to the left'.

A lot has been carried over. The alphabet (alpha, bravo, charlie,...), units (nautical miles and knots).

Right of way rules are similar sailplanes have priority over powered aircraft, otherwise the one on the right has priority and in case of a face to face, you should turn right (or go up/down, but certainly not left)

They didn't completely reinvent navigation for aircraft and a lot of carry over is expected. I'd say port/starboard vs left/right is more of an exception than a rule, generally the same conventions are used when applicable.

Phonetic alphabet is more a radio convention than a navigational convention, and is also used by terrestrial radio users (ie military). Alfa/bravo/charlie was adopted as a NATO standard in the 1950’s; during WWII the US and U.K. used the able/baker/charley phonetic alphabet. And I think aviation adopted the NATO standard before maritime radio.

In sailing, the red/green lights help determine right of way and give way.

  If to starboard red appear, tis your duty to keep clear.

Red Right Returning is used for coming into port in the US. However, in Europe, Australia, New Zealand, parts of Africa and most of Asia it is the opposite.

https://www.cruisingworld.com/red-right-returning/

I think that "red, right, returning" mnemonic is more about the buoys, not the lights on the bow of your boat.

I've always heard, "Hell is on the left."

Pilots tend to not be oriented in any direction other than forward, unlike those aboard a boat who are more likely to be facing all manner of direction and an unambiguous term is needed.

Yep, left, right, up, down, ahead, behind. Although in reference to the parts of the plane you say forward and aft.

They say left and right as others have noted, but the main boarding doors on planes are supposedly on the left for the same reason the left is called the “port”. It appears to be a relic of the flying boat era of aviation.

There are a lot of such relics in aviation, for example distance is measured in nautical miles, speed in knots and the uniforms and ranks are also very much like their naval counter parts.

Nautical miles are used in navigation because one nautical mile equals one minute of latitude when you're traveling North/South, making it a very useful unit of measurement on oceans. Planes use it for the same reason. A knot is simply a speed of one nautical mile per hour, so it's a useful unit for speed when you're using nautical miles for distance.

So I wouldn't call these two specific examples relics, but I agree with you on uniforms & ranks.

Specifically, the nautical mile thing means that any chart with coordinates on it also has a scale in miles built-in.

Doesn't it serve the same purpose, to keep boats/planes going the same direction in the (air)port?

It seems less like a relic and more like applying an already found solution to the same problem.

Naval vessels also can and occasionally do use left/right when talking about some things (like heading changes) where the direction is expressed relative to the current heading, and would not be ambiguously interpretable. It's not common though.