Why do so many people spell dilemma as "dilemna"? Is that accepted as an alternative correct spelling in American English? I don't get it, because wouldn't that make the pronunciation totally different?

I don't thing so, I've never seen it spelled as dilemna myself, who are these people.

Here's the Onelook.com listing for: dilemma

Here's the Onelook.com listing for: dilemna

You be the judge.

I'm sure I've seen this asked in a post here or elsewhere some time ago. I think the general response was that it is just lazy, careless or ignorant. I've never seen it used in British English, and Merriam-Webster on-line, a heavyweight reference for American English, does not recognise 'dilemna' either. The Greek root word has two 'm's.

Mind you, I doubt if 90% of today's British youth have ever heard the word 'dilemma', let alone know what one is. Perhaps if a pop group were to call themselves 'Dilemma'......

You're right, E, this was discussed in that 'other place' we used to frequent pre-AnswerPool.
I can't imagine why there would be any confusion, but there is a plant called 'lemna', a sort of duckweed. Strangely enough, an 18th century edition of Chambers gives that name mistakenly as 'lemma'! So, it seems that there is a long tradition of confusing both 'mm' and 'mn'. There is, of course, no alternative to 'dilemma', as has already been said here.