Small Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Distraction; Confusion
ATC Issue All Types; Inflight Event / Encounter Fuel Issue
Air Traffic Control Provided Assistance; Flight Crew Landed As Precaution; Flight Crew Requested ATC Assistance / Clarification
Environment - Non Weather Related; Procedure
We had an unplanned fuel diversion on our scheduled flight from ZZZ1 to ZZZ2. ATC rerouted us around ZZZ3 Center Airspace due to ZZZ3 Center closure.  Before approaching ZZZ3 Center's airspace; ATC asked us if we'd like to stay at FL430 and reroute; or descend to FL230 and keep the route we had. We determined that we had sufficient fuel to keep our current route and advised ATC that we could descend to FL230.  However; after our descent to FL230; we were assigned a new route that took us around ZZZ3 Center airspace. This added about 150 miles to our original flight plan. Because we were burning more fuel at the lower altitude; and the distance added; we decided to contact Flight Control and ATC to advise of our plan to divert for fuel. We then diverted to ZZZ4 to take on additional fuel before taking our passengers to ZZZ2.In the current environment with COVID-19; we should plan on taking on additional fuel for such abnormalities.
We had to make an unplanned fuel stop on our flight from ZZZ1 to ZZZ2 due to ATC rerouting and closed airspace.  I knew ZZZ Center airspace had some closures and planned extra fuel but it wasn't enough.  As we approached ZZZ Center airspace ATC gave us the option to stay at FL430 and reroute; or descend to FL230 and stay on our current route.  We had plenty of gas so I decided to stay on our current route and descend to FL230.  Once we arrived at FL230 we were then rerouted anyway on an arrival that took us west and added aprox 150 miles to our flight plan.  Because of the added distance and we were burning more fuel at FL230 we decided to contact flight control and divert to ZZZ3 to get more fuel before continuing to ZZZ2. During these uncertain times I will plan to take much more fuel in the event of unforeseen route changes. If I could do it again; I would choose to stay at a higher altitude to conserve fuel.
Air carrier flight crew reported issues with a Center being ATC Zero and having to divert to obtain more fuel to reach their destination airport.