Thousands of frustrated tourists lined up under sweltering heat Wednesday to board airlifts out of the flooded resort of Acapulco while a drenched Mexico braced for new storms.

At least 60 people have died in Mexico since major storms hit opposite coasts this week, the first double onslaught in 55 years, unleashing floods and mudslides still affecting much of the country.

As authorities scrambled to clear landslides blocking the roads out of Acapulco, forecasters said a new cyclone may form on the east coast, while Tropical Storm Manuel regenerated south of Baja California, three days after slamming the Pacific coast.

National civil protection coordination Luis Felipe Puente said the 60 deaths were recorded in 10 states and that the storms have affected almost 220,000 people.

Amid the chaos, thousands of people looted a Costco wholesale store in Acapulco on Tuesday, wading out of the flooded shop with televisions, food and even fridges.

"Unfortunately, there is desperation, but more army and navy troops have arrived," Mayor Luis Walton told MVS radio. "We ask people to remain calm."

The skies finally cleared in the resort after almost one week of nonstop rain, but the heat brought misery to thousands of mostly Mexican holidaymakers standing in massive lines to board military aircraft.

People shouted and shoved each other as some cut the line at an air force base while soldiers handed out water to parched tourists.

Their anger rose as a separate, shorter and quicker line formed for wealthier visitors who booked flights on private jets.

"I ask the government that, since we all pay taxes, we all be treated the same way because the rich and the poor are equal in this tragedy," said Leonor Carretto, 45.

"They should demonstrate we're all equal by letting the little kings bake under the sun for just one hour," added Carretto, whose five-year-old daughter was running a fever after waiting for hours in line.

Some 40,000 Mexican and foreign beach-goers were left stranded in Acapulco after Manuel made landfall on Sunday, followed by Tropical Storm Ingrid on the country's east coast.

The civilian airport's terminal was flooded in knee-high dark water, but commercial carriers began special flights on Tuesday despite the lack of a functioning radar.

"The experience has been a little bit scary because we haven't able to get out," said Tarun Mahrotri, a 34-year-old tourist from London queued up at the military air base.

"We have been more lucky than other people who lost their houses," he said.

Some 5,000 people have been flown out since Tuesday, with Mexican airlines Aeromexico and Interjet offering free flights for people without prior reservations.

The state of Guerrero, where Acapulco lies, has been the hardest hit by the deluge, registering 27 deaths while 15,000 people have been placed in shelters. Helicopter rescued some 1,000 people from rooftops in Acapulco.

President Enrique Pena Nieto warned that the two roads out of the city -- blocked by mud in one tunnel and rocks strewn on roads -- will not be cleared before Friday or Saturday.

After visiting the disaster area, he said opening the roads is urgent "not only for people who have to travel on that road and have to go home, but also because it is obviously an important supply route."

The military has flown 60 tonnes of food supplies and 8,000 liters of water to Acapulco, Defense Secretary Salvador Cienfuegos said.

Some 2,000 tourists have taken shelter in a concert hall, where airlines set up makeshift check-in counters, while 1,000 more were housed in a convention center.

While Acapulco is no longer a favorite haunt of Hollywood stars, and drug gang violence has risen, several tourists were keeping the nightlife alive amid the floods, drinking and eating in bars playing loud music.

"We endured a horrible weekend without light, water or food," said Maria Fernanda Gonzalez, 27, drinking a beer with friends at a beachfront bar.