1 Answer. Ground crew are typically employed by a handling agency, which is a company dedicated to performing ground handling of aircraft (exactly the things you describe).

Airlines use a mix of their own employees and third-party contractors for ground operations, a strategy that varies by airport and airline size. At their primary hubs (for example, Delta at Atlanta or Lufthansa at Frankfurt), major carriers typically employ their own "above-wing" staff (check-in and gate agents) to ensure a consistent brand experience. However, "below-wing" operations like baggage handling, fueling, and aircraft cleaning are often outsourced to specialized Ground Handling Service Providers (GHSPs) like Swissport, Menzies, or Dnata. According to IATA, over 50% of ground handling worldwide is now outsourced. For smaller outstations where an airline might only have one or two flights a day, it is common for the entire ground operation—including the gate agents—to be handled by a third-party contractor or even a "partner" airline. This model allows airlines to achieve "economies of scale" and reduce fixed costs, though it requires strict Service Level Agreements (SLAs) to ensure that the third-party staff meets the airline’s safety and customer service standards.