(CNN) — Nursing mother Lauren Modeen has taken to Twitter to ask why Delta Air Lines forced her to check her breast pump.
Modeen was boarding Delta Flight 2034 last week traveling from Hartsfield-Jackson Atlanta International Airport to Minneapolis-St. Paul International Airport. It was her second flight of the day for a business trip that would keep her away from her baby for four days.
The gate agents wouldn't allow Modeen to board the January 19 flight with her breast pump, which was packed in her standard carry-on suitcase, Modeen said. She also had her purse and a cooler with ice packs to transport her breast milk.
Delta and other airlines allow one carry-on bag and one personal item, such as a purse, for free. Medical devices, strollers and certain other equipment are also allowed and don't count against a traveler's carry-on allowance, according to airline policy.
The gate agent first told her that she needed to consolidate her luggage, even after Modeen says she told the agent that the suitcase included a medical device.
"She then said the computer just gave her a message stating that all passengers starting with me would need to check their bags," Modeen told CNN. "When I later entered the jet bridge, passengers lining up behind me had their suitcases."
Passenger Peggy Flanagan, who says she doesn't know Modeen, said she saw and heard much of the exchange as she was waiting in line to board the aircraft.
"I saw a young woman who seemed really troubled, and the ticket agent continued to say, 'you can't take it on; you're going to have to check your bag,'" said Flanagan, executive director of the Children's Defense Fund of Minnesota.
"She kept saying, 'I have a medical device I need to bring with me on the plane,' over and over, visibly upset," Flanagan told CNN. "The ticket agent and her supervisor, who she eventually called over, were not helpful and not supportive."
"When I got onto the flight, there were at least five available spots in the overhead bins," Flanagan said.
Even if the flight had been full, Flanagan said, they could have asked for volunteers to check their luggage so Modeen's breast pump could be carried on the flight.
"There was no initiative to help her."
Modeen, who couldn't pump for eight hours, finally picked up her breast pump in her suitcase at the Minneapolis-St. Paul airport baggage claim, she said.
"Delta supports the rights of women to breastfeed," Delta spokeswoman Lindsay McDuff wrote in an email. "Breastfeeding and breast pumps are permitted aboard any Delta flight and in Delta ground facilities. We have apologized to the customer for her experience."
Other U.S. airlines have similar policies.
"Southwest welcomes nursing mothers who wish to breastfeed on the aircraft and/or within our facilities," Southwest Airlines spokeswoman Brandy King wrote in an email. "We do not have restrictions on nursing. Breast pumps are considered a medical device and do not count towards the number of carryon items."
"When flying on an American Airlines flight, breastfeeding mothers are welcome to do so during all phases of flight," American Airlines spokeswoman Brianna Jackson wrote in an email. "They are welcome to bring breastfeeding equipment on board as it does not count as a carry-on item."
American's policy isn't online, but passengers can call the reservations number to get more information, Jackson said.
"No prohibitions on breastfeeding for us," United Airlines spokeswoman Jennifer Dohm wrote in an email. She made no mention of the use of breast pumps on United flights.
Modeen says she hopes to increase awareness around women's rights to breastfeed and pump on airlines. With her new Facebook page, Boobs on Board, she wants encourage airlines to post their pro-breastfeeding and breast-pumping policies inside all aircraft.
She says she pitched the idea to Susanna Curtis, Delta CEO Richard Anderson's executive assistant, who she says called her to talk about the incident.
"I told her that on behalf of all nursing moms, I would be extremely grateful if this change happened," Modeen said. (A Delta spokeswoman didn't comment on that conversation.)
Modeen hopes her proposal would encourage airline staff members, increase flying women's awareness of their rights aboard and decrease their anxiety around breastfeeding and pumping aboard, she said.
It's not the first time Delta has faced conflict over breastfeeding. In February, a passenger tried to confirm Delta's breastfeeding policy before flying because her child won't drink from bottles or be covered while eating.
An official Delta Twitter account suggested that she pump before boarding. Later, the account apologized for incorrectly stating the airline's policy and said she was free to breastfeed.