Heathrow airport cargo workers are voting Monday on strike action in a dispute over the use of agency staff and new labor contracts.
The Unite union said the result of the vote by its 300 members at Swissport Cargo will be announced May 4.
The union is required to give seven days notice of strike action, which would severely disrupt cargo shipments at Europe's third largest freight airport after Frankfurt and Paris Charles de Gaulle.
London Heathrow is No. 12 on the JOC list of Top 30 International Cargo Airports
The union decided to ballot its members after Swissport Cargo rejected an offer to refer the dispute to independent arbiters.
"Over a dozen airlines now face the real possibility of heavy disruption to their cargo operations because Swissport management is refusing to genuinely try to resolve this dispute," said Unite official Kevin Hall.
Korean Air, Qantas, South African Airlines, Singapore Airlines and Saudi Arabian Airlines could be affected by strike action.
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