United Airlines has ended a discount agreement with the National Rifle Association, as companies across the US cut ties with the pro-guns group in the wake of the school shooting in Florida.

"United is notifying the NRA that we will no longer offer a discounted rate to their annual meeting and we are asking that the NRA remove our information from their website," the airline said on Twitter.

The move came shortly after rival airline Delta announced a similar move, ending the NRA's contract for discounted rates through their group travel programme.

The NRA's website still stated on Saturday that it had contracted special flight discounts with Delta and United, the second- and third-biggest airlines in the world, respectively.

At least seven other major American companies have cut ties with the organisation since the shooting at Marjory Stoneman Douglas High School, where 17 students and staff members were killed by a lone gunman with an assault rifle.

Florida shooting – in pictures Show all 10 1 /10 Florida shooting – in pictures Florida shooting – in pictures Police arrest a suspect in connection with the shooting at the Marjory Stoneman Douglas High School in Parkland, Florida Reuters Florida shooting – in pictures Parents wait for news after reports of a shooting at Marjory Stoneman Douglas High School in Parkland, Florida AP Florida shooting – in pictures Anxious family members wait for news of students AP Photo/Wilfredo Lee Florida shooting – in pictures Students being evacuated from the school AP Florida shooting – in pictures Students being evacuated from the school Getty Florida shooting – in pictures People gather waiting for word from students AP Florida shooting – in pictures Parents waiting for news on their children AP Florida shooting – in pictures People gather at a hotel where students were taken after the shooting Getty Florida shooting – in pictures Florida Governor Rick Scott speaks to the media as he visits Marjory Stoneman Douglas High School following the shooting AFP/Getty Florida shooting – in pictures Dr. Igor Nichiporenko, Medical Director Trauma, left, and Dr. Evan Boyer, Medical Director, Emergency Services, speak about treating victims and the suspect at a press conference outside Broward Health North hospital AP

As the largest gun-rights lobbying group in the US, the NRA has become a focal point for those advocating for stricter gun control in the wake of the shooting. Several students survivors have backed calls for a boycott of the organisation, boosting the cause on social media.

"#BoycottTheNRA because our lives shouldn’t be measured in dollars," tweeted student Sarah Chadwick, an outspoken advocate for gun reform.

Classmate David Hogg went farther, saying that politicians who took money from the NRA should be voted out of office.

"If our elected officials are not willing to stand up and say, 'I'm not going to continue to take money from the NRA because children are dying', they shouldn't be in office and they won't be in office because this is a midterm year and this is the change that we need," he told CNN.

Car rental companies like Enterprise and Hertz, and moving companies like Allied Van Lines and North American Van Lines have all ended partnerships with the organisation amid the backlash.

NRA chief Wayne LaPierre says elites don't care about America's children in wake of Florida shooting

NRA CEO Wayne LaPierre defended the organisation this week at a major conservative political conference, claiming that gun-control advocates wanted to "get rid of the second amendment" and make Americans "less free".

“They don’t care if their laws work or not,” he said in a speech at the Conservative Political Action Conference. "They just want get more laws to get more control over people."

President Donald Trump also defended the organisation on Twitter, saying their employees were "great people and great American patriots" who would "do the right thing".