+0
Should the plane have crashed, the President would still have survived.

Is the version above an alternative to the 3rd conditional below?

If the plane had crashed, the President would still have survived.

Also, I read these sentences from a site that said they are perfect infinitives. How are they infinitives?

Thanks
+0
English 1b3How are they infinitives?
Bare perfect infinitives, if you insist. They can occur after any modal verb.

should have crashed
would have survived
may have seen
will have done

I think it's just as well to call the whole series of three verbs a verb phrase without messing with the "perfect infinitives" idea.

CJ
+0
As CJ says, the whole series of three verbs is the verb phrase.

Of those three components, two form the bare perfect infinitive; the modal is the gooseberry.

MrP
Students: Are you brave enough to let our tutors analyse your pronunciation?
Comments  
Is the version above an alternative to the 3rd conditional below?-- Yes

Also, I read these sentences from a site that said they are perfect infinitives. How are they infinitives?-- They are not; the site was wrong.
 CalifJim's reply was promoted to an answer.
Yea, I thought it was to do with the modals creating bare infintives.

So the have crashed is a bare perfect infinitive, but a more accepted label is simply the verb phrase?

Ta
Students: We have free audio pronunciation exercises.
 MrPedantic's reply was promoted to an answer.
Yes, of course-- those little bare rascals are hiding everywhere: Let's go, I can't see, etc.