As Nepal tries to recover from the devastating earthquake that left more than 5,000 dead, more than 10,000 injured and nearly half a million displaced, it is relying on international aid for everything from supplies to medics and rescue teams. The world has stepped up: At least 20 countries have rushed to send help, not to mention the European Union, the United Nations and countless NGOs around the globe.

But there is only one way all these groups can enter the country, and that’s through Kathmandu’s Tribhuvan International Airport. While some scheduled commercial flights resumed into Kathmandu the same day of the earthquake on Saturday, both aftershocks and inadequacies of existing infrastructure at the airport -- which is woefully outdated, understaffed and most importantly, offers just one runway for planes to land and takeoff -- have caused vast delays. The result is a bottleneck that is preventing vitally important aid and resources from reaching victims on the ground.

“There is insufficient space and capacity at the airport,” said Clare Doyle, a spokesperson for the United Nations Office for the Coordination of Humanitarian Affairs. “Local authorities, like international responders, are struggling with access problems, lack of fuel and damaged transport infrastructure.”

1 flight out, 1 flight in. It took CSN306S almost 4h to fly 660 km from Dhaka to Kathmandu #NepalEarthquake

— Flightradar24 (@flightradar24) April 27, 2015

Ian Petchenik of global flight tracking service Flightradar24 says that his company has been monitoring flight traffic in and out of the airport since the quake hit. On a normal day, the airport takes a handful of large commercial aircraft coming in from Gulf states like Qatar and the United Arab Emirates, Asian nations such as Korea and Malaysia, and a large number of flights from India.

But now, said Petchenik, the airport is not able to handle the demand of commercial and cargo flights clamoring to get in.

“We’re seeing a lot of holding of flights close to the airport,” said Petchenik, who notes that holding times have ranged anywhere from 10 minutes all the way up to two-and-a-half hours.

Only 8 spaces for large aircraft make for long waits to land at #Kathmandu#NepalEarthquake

— Flightradar24 (@flightradar24) April 27, 2015

There have been numerous accounts in the press of both commercial and charter planes that have been canceled, delayed or diverted, including two Singapore Armed Forces planes that were diverted to India to refuel before trying again on Tuesday.

“Air traffic control [in Kathmandu] is managing the space as best they can to allow as many flights as possible, still do it safely, and unload and reload as quickly as possible,” said Petchenik. Depending on how much unloading is needed, “We’ve seen flights sit on the ground for as little as 30 minutes, some sit on the ground for a few hours.”

In addition to just one runway that is used for both takeoffs and landings, there is very little parking space at the airport for planes to park: It can only hold nine medium and wide-body aircraft, in addition to 17 small planes and 13 helicopters. 

But things could be much worse, said Jo Scheuer, the director of climate change and disaster risk reduction for the United Nations Development Programme, who lived in Kathmandu for many years.

“As bad as this is, it doesn’t meet our worst fears for a catastrophic event hitting the Kathmandu valley. The worst case would have been if the Nepal road network was inoperable and the airport was not functioning altogether,” said Scheuer. “There are longer delays to get planes processed, but we aren’t seeing it to a degree that we need to despair about aid not coming in.”

The real infrastructure challenge, he said, was getting aid to the remote villages and districts outside the Kathmandu valley that are reachable in the best circumstances by underdeveloped, minor roads that have been hit hard by landslides.

The most important flights -- like those bringing in search-and-rescue teams that need to get on the ground immediately -- are prioritized in this situation, said Scheuer, while commercial flights are pushed further down the queue.

That’s evident from the throngs of passengers, including many tourists, who have been stranded at the Kathmandu airport in what many have described as difficult conditions. The passenger terminal has been overwhelmed by people waiting to get out on commercial flights, and the facilities to accommodate them were few and far between.

My friend Casey @modernhiker is stuck at Kathmandu airport after quake. @USEmbassyNepal - any word on getting US citz there help/food/water?

— Joel Rubin (@HarmonyGrits) April 28, 2015

Virginia Guilfoile, an American tourist who was stranded at the airport, described the conditions as “horrendous.”

“[There were] thousands sleeping on the floor…little to eat but biscuits and water for 52 hours. Little to no information from the airlines, disgusting bathrooms -- no water. The toilets don’t flush, sanitation [was] non-existent, there was trash everywhere in the building and a single monitor to post flights,” she told the International Business Times via email.  

According to Scheuer, upgrades to the passenger terminal and additions to the number of parking slots at the airport could go a long way in improving conditions. There’s physically no room to add another airport -- or even another runway -- in Kathmandu due to the geography of the area and the fact that the airport is surrounded by urban development. 

There has been talk of building another airport in the southern part of the country, but in an extremely impoverished nation like Nepal that would almost certainly require some kind of foreign investment. Recently, the Malaysian government put in a bid to operate Kathmandu’s airport, though that proposal is still in its early stages.

For now, said Scheuer, it’s important for tourists and vacationers to keep things in perspective.

“If there are some people like tourists or businesspeople who have to wait a few days to get out of the country, so be it,” he said. “Others stranded at the airport? They’re inconvenienced, stressed and a bit traumatized. But we need to put that inconvenience in perspective with the real need of the people that have truly been affected by the earthquake and the ability of the partners of Nepal to bring in search teams and aid.”