The third conditional is used to talk about past situations that did NOT happen and to imagine a different result in the past.
We use it to express regret, criticism, hypothetical outcomes, or analysis, especially in aviation when reviewing incidents or procedures.
Structure
If + Past Perfect, … would have + Past Participle
Meaning
We use the third conditional to say:
-
“This didn’t happen, but here is what would have happened if it did.”
-
It is 100% unreal past — we are imagining an alternative history.
Example (aviation)
If the pilots had checked the weather earlier, the flight would have departed on time.
→ They didn’t check it early, so the flight was delayed.
Negative forms
-
hadn’t + V3
-
wouldn’t have + V3
Example:
If the engine hadn’t failed, we wouldn’t have diverted.