U.S carriers Delta Air Lines and Alaska Air Group canceled hundreds of flights on Tuesday due to adverse weather conditions and rising cases of the Omicron variant. Delta said it expected to cancel more than 250 of 4,133 scheduled flights on Tuesday, while Alaska canceled 170 flights across its network and warned of more cancellations and delays throughout the week. Total cancellations as of 14.00 ET (19.00 GMT) within, into, or out of the United States stood at 1,034, with 2,694 flights delayed, marking the fifth day of flight cancellations. Delta said it was working to re-route and substitute some planes. Alaska Airlines said as it heads into Wednesday and Thursday, it is proactively thinning Seattle departures by about 20 percent to allow for additional time to de-ice aircraft, a requirement during winter weather. Despite the ongoing disruption, the U.S. Centers for Disease Control and Prevention said on Tuesday it …