It has been 10 hours since US flights resumed after being halted on Friday.
But although some planes are back in the sky, officials have warned that the ripple effects of the disruption could last for days.
Across US airports on Saturday morning, a large number of flights are showing as either delayed or cancelled.
At New York’s JFK airport, for example, 103 due to depart in the next two hours are are cancelled and 17 are delayed - meanwhile, 90 flights are listed as on time.
Officials have said the disruption could last for days, but hope the situation should return to normal by Thanksgiving.
Boston Logan International Airport is currently the most disrupted airport in the world, according to Flightradar24 data, external.
The top nine spots on the flight-tracking website’s live list of the most disrupted departures are all taken by US airports.
Boston is followed by New York’s JFK and Ronald Reagan National Airport in Washington DC.
Flightradar24 assigns a value between 0 and 5, taking into account the number of delayed and cancelled flights, as well as the average delay. The higher the number, the worse the disruption.
The 10th most disrupted airport is Guadalajara International Airport in Mexico.
Amsterdam's Schiphol airport is showing delayed flights from Philadelphia and Atlanta. Flights from Miami and New York to Madrid's Barajas airport are also disrupted.
Paris's Charles de Gaulle airport is showing cancelled flights from Dallas and Chicago. Several others are delayed.
A flight leaving Frankfurt airport for Atlanta at 10:30 local time (09:30 GMT) was cancelled, as was a 10:55 flight to Detroit.
Seoul's Incheon airport in South Korea is reporting delayed arrivals from Honolulu and Los Angeles. Departures to Minneapolis and Seattle are also running late.
The grounding began at around 16:00 EST (21:00 GMT) on Friday and lasted more than four hours - here's a timeline of how it unfolded.
Transportation Secretary Sean Duffy said the ripple effects could last for days - it was the longest ground stop in the US since the one after the 9/11 attacks in 2001.
On Saturday morning, some transatlantic flights from the UK have also been disrupted, with passengers warned of "follow-on disruption"
Officials say the incident was caused by a "telecommunications outage" and place the blame on old systems.
