Ending sentence with "supposed to"

Solution 1:

to be supposed to do something: be required to do something because of the position one is in or an agreement one as made

• I am supposed to be meeting someone at the airport.

So, you can understand the sentence by re-writing it as:

He arrived ten minutes earlier than he was required to.

It is completely correct.

Solution 2:

This is perfectly correct. If you don't like the sound of it you could make it more elegant (in my opinion) by changing it to:

He arrived ten minutes earlier than he was supposed to have done.

Solution 3:

It's acceptable. "Supposed to" has always looked strange to me in writing. You could extend it out to "...supposed to have." but I don't really think there's much helping the feeling except getting used to using the phrase.

Solution 4:

I guess it does break the (pointless and stupid) rule against ending a sentence with a preposition. Despite that, it seems like a perfectly good sentence to me. That would be very hard to re-word to avoid that problem.

You could say, "He arrived ten minutes earlier than he was supposed to arrive," but that sounds clumsy with "arrive" used twice in such a brief space.

You could, I guess, say, "He arrived ten minutes earlier than he was expected" or some other totally different word.

I'd keep it as is.

Solution 5:

How about:

He arrived ten minutes earlier than he had planned.

It has a slightly different connotation, but if you think "supposed to" is a bit unwieldy perhaps this works better?