MR String model: Constraints Maintenance constraints Satisfied by variable definition Cover constraints Each flight must be assigned to exactly one string Balance constraints Needed only at maintenance stations Fleet size constraints The number of strings and connection arcs crossing the count time cannot exceed the number of aircraft in the fleet 2/212021 Barnhart 1.206J/16.77J/ES D 2 15J2/21/2021 Barnhart 1.206J/16.77J/ESD.215J 6 MR String Model: Constraints • Maintenance constraints – Satisfied by variable definition • Cover constraints – Each flight must be assigned to exactly one string • Balance constraints – Needed only at maintenance stations • Fleet size constraints – The number of strings and connection arcs crossing the count time cannot exceed the number of aircraft in the fleet