The bulk of the some 2,500 passengers stranded at Shanghai Pudong International Airport Thursday finally departed during a four-hour window in the wee hours of the morning, after heavy fog conditions caused hundreds of cancellations and delays for air, sea and rail travel this week.

The volume at the city's eastern airport was triple that of normal daily operations Thursday, with 138 flights arriving and departing from the Pudong airport between the hours of late Wednesday night and early Thursday morning, when heavy fog cleared and allowed operations to resume to normal.

"About 30 of the flights that took off between midnight and 4 am Thursday were added to help clear the crowds of passengers that had been waiting here for hours due to the countless delays and cancellations," Su Weiwei, a press officer for Shanghai Airport Authority, told the Global Times Thursday.

But Su said that while operations have resumed, the situation at the Pudong airport would still be a bit chaotic for the next couple of days since the past few days of severe fog has created a backlog of passengers from some 890 affected flights over the past three days. 

At Yangshan Deep Water Port, the situation was not as promising as foggy weather was still affecting the waters Thursday afternoon. While 20 ships were able to dock and leave the port early in the day, the port was forced to close again in the afternoon.

The port saw the worst of the fog this week, with only 43 ships being able to enter and set out over the past three days, not even a third of the volume that passes through during a normal three-day period. Port authorities said that they will keep monitoring the situation.

High-speed trains, meanwhile, resumed regular operations in the city Thursday, after canceling three trips due to fog this week.

The city's weather authorities said Wednesday that the fog was expected to clear by Thursday due to a cold air pressure moving in from the north. The system will continue to work its way southward today, authorities said Thursday. 

Miranda Shek contributed to this story