By Todd Benson

SAO PAULO, July 27 (Reuters) - The main runway at Brazil's busiest airport reopened on Friday, 10 days after a passenger jet skidded off its rain-slicked surface and crashed, killing almost 200 people in the country's worst aviation disaster.

Authorities opened the recently repaved runway at Sao Paulo's Congonhas Airport even though it has not yet been entirely grooved to drain rainwater and prevent planes from slipping when they touch down.

Landings will be restricted in wet weather until the surface is completely grooved, which could take weeks. In the meantime, flights arriving in heavy rains will touch down on the back-up runway at Congonhas or be diverted to the city's Guarulhos International Airport.

The main runway at Congonhas was reopened after being inspected by new Defense Minister Nelson Jobim, who was appointed on Wednesday to overhaul Brazil's ailing aviation sector. The defense ministry and the air force oversee airports and air traffic in Brazil.

The runway, one of the shortest in the country, has been at the center of a fierce debate over air safety since an Airbus A320 <EAD.PA> carrying 187 people crashed in a botched landing attempt on July 17.

The plane, flown by Brazilian carrier TAM Linhas Aereas <TAMM4.SA><TAM.N>, barreled off the landing strip in the rain and rammed into a cargo terminal and gas station, bursting into flames. Everyone on board and at least 12 more on the ground were killed in the accident.

Authorities are investigating if the runway, which is known for being slippery, was unsafe for landing in the rain. Investigators are also trying to determine if possible pilot error and mechanical problems contributed to the crash.

Air travel in Brazil descended further into chaos after the accident, the second major aviation disaster in the country in 10 months. Last September, 154 people were killed when a Boeing 737 <BA.N> clipped wings in midair with a private jet and crashed in the Amazon jungle.

The closure of the main runway at Congonhas after the TAM crash forced airlines to cancel hundreds of flights and caused a ripple effect of delays around the country. Since then, revolts at ticket counters have become routine and some airlines have even urged passengers to travel by bus.

Air travel was slowly starting to return to normal on Friday, with fewer delays and cancellations around the country, according to Brazil's airports authority Infraero. At Congonhas, however, 40 percent of all flights were canceled on Friday morning before the runway reopened.

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