The readiness of an aircraft for flight is ensured by:

The readiness of an aircraft for flight is fundamentally ensured by routine checks and verified maintenance procedures. This process involves a series of inspections, tests, and maintenance tasks that are meticulously documented and follow established protocols to ensure that every system of the aircraft is functioning properly before any flight.

Routine checks include pre-flight inspections, scheduled maintenance, and regular component replacements or upgrades that are all part of the aircraft’s maintenance management plan. These procedures are designed to identify potential issues before they become serious problems, thus ensuring safety and reliability during operations.

Verification of maintenance procedures is equally important because it holds technicians accountable and ensures that the work performed adheres to the manufacturer's and aviation regulatory standards. This systematic approach to aircraft maintenance directly contributes to the aircraft's overall operational effectiveness and flight readiness, making it the optimal answer to the question posed.