Dry chickpeas over paper towels until completely dry. Place chickpeas, onion, parsley, flour, cumin, coriander, cayenne, salt, and pepper in a food processor. Pulse until combined and starting to resemble a coarse paste.
Place falafel mixture in a bowl and cover. Refrigerate for at least 1 hour. While falafel is chilling, cut out 2-inch circles from the pita bread. Set aside.
Pinch off a heaping tablespoon of falafel mixture and roll into a ball. Flatten slightly. Continue with remaining dough. Spray the falafel lightly with cooking spray.
Heat air fryer to 400° F. Working in batches, cook falafel until crispy and cooked through (about 10-15 minutes).
Assemble falafel bites by placing a falafel on a pita bread round, and topping with a dollop of tzatziki. Enjoy!