What are two things that must be completed prior to hooking up a tower to an aircraft?

Prior to hooking up a tower to an aircraft, it is critical to ensure that both the tow bar and by-pass pin are inspected. This is essential for safety and equipment functionality. The tow bar must be in good condition, with no signs of wear or damage, to ensure it can handle the forces involved in towing the aircraft. The by-pass pin serves as a safety mechanism that prevents unintentional release of the tow bar connection; it must be correctly positioned and functioning to guarantee safe operations. Failing to complete this inspection can lead to serious accidents during towing operations, making it a fundamental step that must not be overlooked.

Other choices, while important in various contexts of aircraft handling and maintenance, do not represent the immediate and critical safety checks required specifically before connecting a tow bar to the aircraft.