STARTS US OFF FROM CHICAGO'S O'HARE AIRPORT. SHAQ, GOOD EVENING. >> Reporter: GOOD EVENING, TOM. YOU SEE THE FOLKS BEHIND ME PREPARING TO TRAVEL. AS THE TSA SAYS IT'S PREPARED TO SCREEN 3 MILLION PEOPLE AT CHECKPOINTS NATIONWIDE MAKING TODAY THE BUSIEST DAY OF AIR TRAVEL THIS HOLIDAY WEEKEND. TONIGHT, SEVERE SUMMER WEATHER CLASHING WITH THE LABOR DAY WEEKEND TRAVEL RUSH. A TORNADO RIPPING THROUGH MINNESOTA YESTERDAY. TACKLING TREES AND KNOCKING OUT POWER TO THOUSANDS. >> HE SHUT THE DOOR AND IT WENT BOOM, BOOM, BANG. I SAID, LET'S GET THE DOOR CLOSED. >> Reporter: A MESS ON THE ROADS IN PENNSYLVANIA TOO. FLASH FLOODS CAUSING THIS MASSIVE SINKHOLE. >> IT'S COMPLETELY GONE. I'VE NEVER SEEN ANYTHING LIKE THAT. >> Reporter: MILLIONS UNDER THREAT AS THUNDERSTORMS PLOW THROUGH MAJOR TRAVEL HUBS LEADING TO FLIGHT DELAYS IN RALEIGH, NEW YORK, AND CHICAGO. ACROSS THE COUNTRY MORE THAN 200 CANCELLATIONS OVER 5,000 DELAYS. >> ANXIETY LEVEL FEELS A LITTLE HIGHER SO DEFINITELY TAKING A COUPLE OF DEEP BREATHS. >> Reporter: A RECORD LABOR DAY TRAVEL WEEKEND AT CHICAGO'S O'HARE AIRPORT WHERE WE SPOTTED OLYMPIC CHAMPION SIMONE BILES AND HER HUSBAND, BEARS SAFETY JONATHAN OWENS WHO SAID THEY WERE HEADED HOME. OFFICIALS SAY PLAN AHEAD. >> WHAT DO YOU SUGGEST PEOPLE DO. >> MAKE YOUR TRAVEL RESERVATIONS EARLY, ARRIVE EARLY AND PATIENCE AS WELL. >> Reporter: THE TRAVEL RUSH EXTENDING TO THE ROADS WITH SOME RELIEF AT THE PUMP. >> I'M IN ATLANTA AND GAS PRICES ARE $3.26 PER GALLON. BELOWE THE NATIONAL AVERAGE OF $3.36 WHICH IS DOWN ALMOST 50 CENTS FROM THIS TIME LAST YEAR. >> Reporter: A HOLIDAY WEEKEND BLITZ CAPPING OFF A