In British spelling, verbs ending in a vowel plus l double the l when adding endings that begin with a vowel. In American English, the l is not doubled:
Travel → travel
Travelled → traveled
Travelling → traveling
Traveller → traveler
Some nouns that end with -ence in British English are spelled -ense in American English:
Defence → defense
Licence → license
Offence → offense
Some nouns that end with -ogue in British English end with either -og or -oguein American English:
Analogue → analog or analogue
Catalogue → catalog or catalogue
Dialogue → dialog or dialogue