If he traveled more often, he would know that the planes are delayed sometimes.
Past unreal conditional structure:
If she hadn't forgotten her passport, she wouldn't have had problems at the airport.
Present factual conditional structure:
If you buy the plane tickets on the internet, you will get a discount.
Present unreal conditional structure:
If clause = If + past perfect; result clause = would/could/might have + past participle
Present unreal conditional
If clause = If + simple present; result clause = will/be going to + base form, may/might/can + base form
Present factual conditional
Past unreal conditional
If clause = If + simple past; result clause = would/might + base form
