More than 2,000 postcards completed by members of the two protesting unions at NATS – Prospect and PCS – will be handed to a representative of the UK government's aviation minister, Simon Burns.
Under the Single European Skies (SES) proposals, the European Commission wants to halve Air Traffic Management (ATM) costs by 2020, resulting in huge job losses across Europe.
The protest marks the start of the European Transport Federation's campaign against the SES proposals, which will see air traffic unions across Europe either take industrial action or organise demonstrations.
NATS staff fear that the proposals from the commission will mean the service provided to airlines and passengers will suffer and put safety at risk through over-stretched air traffic management resources.
They also warn that Single European Skies could impact on the UK's ability to control its own airspace and are calling on the government to oppose the changes.
Emily Boase, Prospect National Secretary, said: "The UK is one of the most efficient providers of air traffic control services, with the least delays in Europe. All this will be put at risk if the commission's proposals are carried through."
Jeremy Gautrey, PCS Aviation Group Secretary, said: "There is no bigger risk to safety and service delivery in air traffic than cuts to air traffic management staff. Cuts in staff and forced redundancies will be met robustly with industrial action by ATM workers across Europe."
PCS represents 1,000 NATS staff; Prospect represents 3,000 people working as controllers, systems engineers, scientists and specialists. Both unions are affiliated to the European Transport Federation.