After Farrier saves the lives of many on the sea coast in Dunkirk, and his fuel is off, he lands smoothly in the enemy zone and puts the plane on fire and gets himself captured.
Why did he hesitate to open the parachute and escape?
I'm not a pilot but from my readings they'd much rather make a safe landing than jump from a plane they can land even if there was the possibility of capture.
Jumping/parachuting from a fighter was not an easy process during WW2. Firstly, you had to be a lot higher and climb out of the aircraft while still flying level (which is hard to do since there was no automatic pilot) nor were their ejector seats in early WW2.
In general, it involved (if my reading is correct), for the most part, inverting the aircraft and falling out.
Here's a reddit thread comment
So, your cockpit is not on fire, you have a few seconds to spare, you can act methodically instead of frantically.
First of all, jettison the canopy. Don't just open it, because due to some odd factors it might close back again. We have time to spare, but no time to lose.
You also need to unbuckle your seat-belts and don't forget to detach your radio cable and oxygen supply. If you forget, it might prevent you from leaving the aircraft. Again, no time to lose. Now, do you have aileron authority? You do? Great, perform a half barrel roll. Now you will simply fall out of the cockpit, also minimizing the risk of hitting the vertical or horizontal stabilizer (though the risk will always be there, this is exactly what killed Hans Joachim Marseille, in my opinion the best fighter pilot of WW2).
If you cannot roll the plane on its back, you have to climb out of the cockpit onto the wing and just jump. Be careful as the air striking your body will try to force you back into the cockpit. If one wing is angled downward, you can attempt to slide down on it just a little bit to avoid the stabilizers.
Now, you're in the air. When do you open the chute? It depends. You might want to do it immediately, but not necessarily. Say we're in the Battle of Britain. If you're an Allied pilot and there are Luftwaffe planes near, wait as long as you can since they might attempt to shoot you out of the sky. Also, if you're near the Channel and the wind is blowing towards it, wait as long as you can so as not to be blown over the water. And if you're falling from very high up, you might want to wait a bit so as not to die of boredom during the long descent.
Gliding an aircraft, out of fuel, would have been much safer.
Even if he did jump..where's he going go? He's essentially alone in occupied France...he's going get captured anyway.
He once thought about opening his parachute. But on a second thought, he did not want the Allied to see the aircraft go down, which would affect the Allied's spirit negatively. Then he decided to sacrifice himself.
Other answers are just twisting facts to convince people that the plot of the movie was technically correct.
I think it was totally a play with emotions. Imagine he actually jumped from the aircraft and survived. You know that there were really high chances of survival if you are not blinded by your faith in the technical aspects of the plot.
That would have been a dull(but happy) ending. The makers of the movie probably felt it to be a better ending to show a hero saving a lot of people and then surrendering himself in the hands of the enemy.