If a strike were to go ahead, it could coincide with the main school summer holidays. But the airline says a strike would have “no effect”.
Unite represents 38 passenger service agents employed by Stobart Aviation Services Ltd, which has the easyJet contract at the Essex airport.
The union’s regional officer, Mark Barter, said: “While workers employed by other companies at Stansted are being paid up to 20 per cent more for doing the same job, our Stobart members work unpaid overtime, experience staffing issues and lack of basics, such as drinking water, during their long shifts.
“It is no wonder there is a massive turnover of staff at Stobart Aviation Services, as they feel undervalued and are paid dismally.
“If our members working on the easyJet contract vote to strike, this will cause severe disruption for the airline’s passengers trying to check-in for their summer holidays.”
The ballot closes on Tuesday 2 July, but Stobart has now agreed to meet the union on Thursday 20 June.
A spokesperson for airline said: “easyJet is aware of the proposed ballot on industrial action by Unite for check in staff at London Stansted Airport.
“If industrial action is confirmed we will have contingency plans in place so that there would be no impact on our passengers.”
At Glasgow airport, members of the Unite union are planning five four-hour strikes up to the end of June: on Friday 21 June, 8.30am-2.30pm; on Monday 24 June, 6-10am; Wednesday 26 June, 10am-2pm; Friday 28 June, 9.30am-1.30pm; Sunday 30 June, 5-9pm.
Security offices, firefighters, operations officers and engineering technicians are involved in a dispute over pay and pensions.
In addition, staff at Aberdeen airport – which is owned by the same company as Glasgow – are striking on the same issues on 27 and 28 June, both 6-10am.