WASHINGTON, (Reuters) – Haitians ravaged by the  earthquake that devastated their capital this week begged for  food, water and medical assistance as the world rushed to bring  aid to survivors.

Foreign governments and aid agencies seemed to mobilize  quickly to get relief supplies to victims of Tuesday’s quake,  but they have encountered obstacles typical after a natural  disaster.

Why is it taking so long to get aid to people in need?

Haiti’s airport was damaged by the quake and the control  tower completely knocked out, making it impossible for relief  aircraft to land safely in the first hours of the disaster.

A U.S. military team has since reopened the airport, which  has become congested with aircraft carrying supplies for  different aid agencies and the United Nations. In addition,  hundreds of people have gathered at the airport to try and get  out of Haiti, making the situation more chaotic.

Some supplies destined for Haiti have had to go overland  from neighboring Dominican Republic. Aid groups have reported a  journey of up to 10 hours or more before they reach Haiti. Once  at the border, they have had to deal with long lines of people  and vehicles waiting to cross into Haiti.

Aid agencies already on the ground in Haiti, and which  would have been best suited to help, also suffered losses and  were unable to get word to their headquarters because  telecommunications were down.

Why can’t the u.s. military just airdrop supplies?

U.S. Defense Secretary Robert Gates has said dropping water  and food from the air could cause riots and chaos.

There is also a danger that air-dropped parcels would get  into the hands of the wrong people who would try to sell them,  preventing supplies from getting to those in need.

General Douglas Fraser, commander of U.S. Southern Command,  said the airport, now under U.S. control, can handle about 90  flights a day, but he said that was not sufficient to meet the  needs of the Haitian population.

If the food is at the airport, why isn’t it moving?

Supplies coming through the airport are held up because  roads leading into the capital Port-au-Prince are impassable  and strewn with rubble and scattered with decomposing bodies.  Much of this has to be cleared before aid can flow. The only  way to get aid to people is by helicopter.

And what about water? does that get flown in?

The earthquake destroyed whatever water supply there was in  much of Haiti and aid groups are having to truck or fly in  clean water. In some instances, aid groups like Oxfam said they  have had to fly in engineers and generators to help restore  water supplies.