Is it grammatically correct for a pilot or airline cabin crew to say "welcome on board", rather than "welcome aboard?" Is there a difference?

3 Answers 3


On board describes that something is aboard a vessel, i.e., the location of something or someone.

Onboard is one word (sometimes hyphenated—on-board) when it comes before the noun it modifies (e.g., onboard radio, onboard computer). Elsewhere, writers usually make on board two words. For instance, one might write, “We brought a radio on board so we could have an onboard radio.” Reference: "Onboard vs. on board", from grammarist.com

It's rather an idiomatic phrase (or a quasi-adverb).


  • There are no medical physicians on board.
  • Smoking is not allowed on board.

Aboard modifies an action and is often followed by reference of the vessel, e.g. to step aboard a something.

Grammarist supplies several examples (same reference as above):


Justin boasts an onboard 3-D camera system for analyzing points in space. [Wired News]
Although the airline grabs headlines for threatening to charge people to use onboard toilets or save money by dumping co-pilots, it normally turns to conventional ruses. [Guardian]
At one highway fill-up, the onboard computer showed I had a range of 880 km. [National Post]

On board
President John F. Kennedy called Shepard after he was taken on board the aircraft carrier that retrieved him from the ocean. [USA Today]
San Pietro was being sailed by the remaining crew on board. [Stuff.co.nz]

  • I like your answer, but didn't get the difference you explain between on board and aboard.
    – Quidam
    Oct 31, 2019 at 12:48

"aboard" is only a contraction of "on board". May be pilots prefer "on board", but actually there is no difference between the two variants.

  • 6
    No, it's not a "contraction". The a- prefix occurs in many words (abed, abreast, ashore, ajar, asleep, etc.). Sep 15, 2014 at 18:12
  • 4
    It quite obviously does not! The a- prefix/preposition has been validly used in English for centuries with the general sense of expressing position within, situation, etc. The fact that you can in most contexts replace it with a different preposition doesn't mean the a- form is some kind of later derivation. Sep 15, 2014 at 18:25
  • 2
    @FumbleFingers It actually does. The a- prefix is etymologically just a development of unstressed of, in, or on. I agree that they’re not contractions, but aboard does come from on board, and abed does come from in bed. The fact that the ‘full’ forms can still be used is just because both the noun and the preposition are still both part of the language and the collocation is literal and obvious enough to be remade productively. This isn’t always the case: anew comes from *of new, which is less literal and has disappeared from the language. Sep 15, 2014 at 20:52
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    @Janus: Granted, if we go back far enough the a- prefix did indeed derive from unstressed on (so in any case that leads to abed = on bed, not in bed). But it's hardly in the same league as saying "it's is a contraction of it is", which is how I read this answer. Interestingly, OED says of aboard Probably partly a prep.1 + board n., and partly Middle French a bord on a ship (1393 or earlier; French à bord. May be [sic! :] it's arguable either way. Sep 15, 2014 at 21:15
  • 1
    @FumbleFingers That’s why I said I agree they’re not contractions. They’re just forms whittled down by the hands of time until no longer recognisable, like so many other words. (Incidentally, OE on and in were often very poorly distinguished, since both were often reduced to just a, probably representing [ə]; whether abed is originally from on bed or in bed is all but impossible to say now.) Sep 15, 2014 at 21:19

We are on board the plane because we have boarded the aircraft.

Aboard the ship, we watched the waves.

Perhaps a bit silly, but:

As you are now on board, welcome aboard the our vessel.

As you are now aboard (the vessel) let me say welcome on board!

I don't see any grammitical difference, rather it seems to be usage as Fumble (hi ya Fumble :) says. (And there's Amid ship - center of ship.)

It would be even more silly, but grammatically correct, to say:

As you are now aboard, let me say welcome aboard.

I wonder if the word 'board' derives from the planks / boards used from dock to ship to enter the vessel?

"Arrr matey, Howard, walk the plank off board!"

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