More than 230 schools either delayed or canceled classes Tuesday due to icy conditions on North Texas roadways that led to hundreds of crashes and four deaths, including a Dallas firefighter who died after being knocked of an interstate ramp.

While covering a fatal crash Tuesday morning, NBC 5's Kendra Lyn witnessed a string of crashes as drivers spun out of control along a slippery stretch of southeast Loop 820 near Anglin Drive in Fort Worth. Watch the video here.

In crashes at that location, officials said five people were injured and one man, 31-year-old Jeffery Rozas, was ejected from his vehicle and killed. Read the full story here.

Earlier that morning, a driver in Fort Worth, later identified as 56-year-old Kenneth Jones of Azle, was killed when he lost control of his sport utility vehicle on an icy bridge and slammed into a tree along the 5500 block of Cattlebaron Drive. The single-vehicle crash was reported at about 5:30 a.m.

A 16-year-old driver, identified as Katelyn ShyAnn Hooper, was killed in a crash on Farm-to-Market 156 south of state Highway 114 in Denton County on Monday. Texas Department of Public Safety troopers said the Hooper's car was traveling south on FM 156 when she lost control, crossed the centerline and was struck by a pickup truck. Hooper's family said the driver of the truck lost control. A second teen in the car is listed in critical condition. Read the full story here.

In Arlington, a crash involving up to 20 vehicles was reported Monday at Collins Street and Green Oaks Boulevard. Also on Monday night, Denton police closed U.S. Highway 380 near Loop 288 so that sand trucks could treat icy patches.

“For the first time since I have been doing this for five years, we had to shut the trucks down because we didn’t want to tear up the equipment. This has been a bad winter,” said Lou Zion, of Pursur Towing.

Overnight Monday, the Fort Worth Police Department tallied 375 crashes between 5 p.m. Monday and 8 a.m. Tuesday.

MedStar reported it responded to 32 motor vehicle crashes between 6 p.m. and 9:30 p.m. Monday. MedStar also said they were prioritizing 911 calls to address the most life-threatening first and any calls where the patient may be outside without shelter from the cold.

Dallas Firefighter Killed After Fall From Bridge

On Monday night, a Dallas firefighter was thrown from a bridge while at the scene of a crash on a highway flyover.

Dallas Fire-Rescue said 40-year-old William Scott Tanksley was assisting a motorist when a passing car slid on the ice and struck him, forcing him off the Spur 408 overpass and onto a bridge below. Read the full story here.

Flight Cancellations

According to Flight Aware, as of 4 p.m. Tuesday, 205 flights departing Dallas-Fort Worth International Airport had been canceled and another 86 were delayed. Inbound, there have been 174 cancellations at DFW and 78 delays.

At Love Field, six departing flights have been canceled and 64 have been delayed. Inbound there have been five cancellations and 64 delays.

More than 200 flights were canceled on Monday and over 600 flights were delayed.

Schools Delay, Cancel Classes Due to Weather

Many schools in Denton County are closed due to the icy conditions, including the University of North Texas and those in the Denton, Krum, Argyle and Northwest independent school districts.

Many more districts and organizations are delayed or closed on Tuesday, CLICK HERE for Latest School Closings and Delays

A Winter Weather Advisory is in effect for most counties in North Texas through 6 p.m. Tuesday. CLICK HERE for Current Severe Weather Alerts

NBC 5's Kendra Lyn, Brian Scott and Julie Fine contributed to this report.