Airlines will have to meet these schedule requirements to get coronavirus aid

When Congress passed a $50 billion aid package for airlines last week, the legislation suggested that carriers would be required to maintain a minimum level of service as a condition of receiving that aid.

On Tuesday, the Department of Transportation announced more details about exactly what would be expected of airlines.

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The basics

The guidelines, which are based on each airline's service pattern before March 1, fall under three broad categories:

1. Cities served five times per week or more would need to maintain at least one daily flight per day, a minimum of five days per week.
2. Cities served with less than five flights per week would need to maintain at least one weekly flight.
3. Cities with flights to multiple other points could see service reduced to a single destination, so long as that schedule complied with the two guidelines above.

Practically speaking, here's what that could look like:

1. American Airlines flew roughly hourly every day between New York (LGA) and Dallas/Fort Worth (DFW), and it also offered many DFW flights from JFK and Newark (EWR), as well. That schedule could be reduced to a single NYC-DFW round-trip on at least five days each week. Under the guidelines, that would fulfill American's service requirements for both cities.
2. If United Airlines flew three times per week between Denver (DEN) and Flagstaff (FLG), and that represented the airline's only service to Flagstaff, that schedule could be reduced to one flight per week.
3. Delta had multiple daily flights from Green Bay, Wisconsin (GRB), to other cities, including Detroit (DTW), Minneapolis (MSP) and Atlanta (ATL). That service could be pared down to a single flight, at least five times weekly, between Green Bay and one of the other cities, such as Detroit. Delta could also choose to operate at least five flights weekly from GRB, and distribute them to among various destinations.

Related: What the airline aid package means for travelers.

These guidelines are open for public comment through April 2, and have not yet been finalized. Once enacted, the rules will apply to any airline that seeks aid under the CARES Act, for either loans or grants.

In the weeds

The rule will consider regional service to fulfill the obligation of the marketing carrier. So, American Eagle flights will count toward American Airlines' minimum service requirements, However, if SkyWest, for example, operates any non-cobranded flights, it will be responsible for maintaining its own minimum service on those routes if it accepts government aid.

Airlines will also be allowed to request exemptions from these guidelines if they determine that some cities do not warrant the minimum required service given current demand.

Read more: An in-depth analysis of the $50 billion aid package to airlines.

Charter and air taxi operators are exempted from these guidelines. All-cargo carriers are technically covered by the legislation, but the DOT has opted not to enforce minimum-service guidelines on cargo operations, citing a recent increase in demand for cargo capacity.

Once finalized, the guidelines will remain in place through Sept. 30.