Could go with "airplanes" which has a more conventional plural form and is much simpler and clearer in cases like this where we know full well what specific type of aircraft we're talking about.
It's an artefact of where English gets the word "craft" from. In general in English the plural of uncountable things is the same as the singular. For example, the plural of sugar is sugar (sugars in English implies a group of different types of sugar). The word craft comes to English from Germanic (kraft). The meanings of these two words (English craft vs German kraft) diverged over time. In English the word has a meaning similar to that which is made or the manner in which it is made. Whereas in German it means the means by which something is made (i.e. power, in both the physics and non-physics sense). For example Kraftwerk in German means power station.
Since the "means by which" is uncountable (craft) then the plural should be the same as the singular; i.e. one craft, many craft. This also applies in English to older agglutinates like aircraft. Newer agglutinates (for example laptop) are far less likely to follow this rule; one laptop, many laptops.
English, due to its muddled heritage and well intentioned but half informed linguists over the years, is a very messy language.
I wonder how the craft word was adapted to mean the boat object.
I think for river travel it was common to build a boat/raft to make a journey and then break it up at the destination. In that context maybe the object of the boat was secondary to the act of making the boat. And at some point boats became more personified and thought of as things in their own right.
A couple other suggestions, although still not certain:
> Use for "small boat" is first recorded 1670s, probably from a phrase similar to "vessels of small craft" and referring either to the trade they did or the seamanship they required, or perhaps it preserves the word in its original sense of "power."
I suspect it was a shortening of watercraft. According to wiktionary the use of the word for water vessels was originally used for smaller loading craft. So using the older Germanic meaning of "by means of", the phrase "it got here by watercraft" could be translated as "it got here by means of water". One could assume that it wouldn't take much for the word to go from preposition to noun; especially in the context of agglutinates and abbreviations.
The English word "boat" comes directly from German; "das Boot".
Same... at least they should put an S to aircraft... but then again maybe they hit the strict character limit...