First of all, everybody gets a window seat on the ride from Pheriche to Kala Patthar, which is a highlight ride of the trip. Meanwhile, on the flight from Kathmandu to Lukla till Pheriche, three people can have window seats at once. Because of that, your pilot will arrange (alternate) the seating so that everybody gets to have a window seat either on their way to Lukla and Pheriche or the way back.