Breath....
DP goes in, asks for the passport and then with evidence provides the landing times.
DP then states he believes its in the best interest of the child to be returned at 6pm, having had rest and food in preparation for the hand over.
It's then up to the other party to present evidence of why a 6pm drop off is not suitable. If she states I have a holday booked for the drop off day with a flight leaving at 16:35.
Then DP counters with 3 options.
Mother can collect from airport upon landing and the passport handed back in preparation for the departure later in the day.
Mother collects from DP house at say 1pm in preparation for the flight and to hand back passport. As it's in the child's best interest to have some sleep and rest and food before departing on another flight.
3rd and final option is DP returns child to the airport in time for departure at say 1pm. Again in the child's best interest to have some sleep and food before another airport departure.
Leave it to the judge after that.
Mum either way is going to have to drive to airport or DP's house.
She can do the legwork.
If mum counters with dropping child off at 10:30am to her. DP counters with he does not believe 3hours sleep is in the best interest of the child when the other available option can give her a 7hour or so sleep in preparation for travel.
Simple. Let the judge decide.