Every airline will be different but as posted day or two ago the 1.) Lease 2.) Payroll 3.) Fuel 4.) Airport / APD / ATC / etc wil likely to be the highest in value terms.
Aircraft lessors will have to take a pragmatic view of rescheduling payments because failing to do that means Airlines start collapsing and there is not a who new range of clients out there will to take aircraft on, hence still owe but instead of paying next quarterly payment (not sure whether it is like property where rent paid 4 times a yr in advance) debt gets parked until can be paid. Lessors taking a hard line will likely find that other airlines / govts etc act against them like banking license etc. Basically everybody in same boat so consistent approach sought.
Employess............. likely to be laid off, Govt will then have to fund via welfare system
Fuel............. not using then not paying and contracts for certain levels will just be rolled over, bearing in mind fuel price halved then oil companies will want airlines held to contracts at €75 a barrel, hence play ball.
Govts etc............... possibly more problematic but can see airlines taking a lot longer to pay, airports which do not have aircraft stationed there and no flights coming in for foreseeable future may not be paid for a long time. Pay those whom you need to pay, rest will pay eventually. Some airports will go bust.
We should also remember the thousands of staff who work in airports, many already on reduced hours and many will lose their jobs.
Bottom line is to manage cash flow now.