Is airplane correct in British English?
Airplane would be understood by users of British English, but it is likely to be considered an incorrect spelling or an “Americanism.” Although there is no difference in meaning between aeroplane and airplane, you should spell it to remain consistent with the spelling in the rest of your document.
The QuillBot Grammar Checker has selectable regional language options, so you can be sure you have the correct spelling of aeroplane/airplane.