The Bulgarian Socialist Party (BSP) filed in parliament on Thursday a proposal to cancel a tender for awarding a 35-year concession contract for the operation of Sofia International Airport, according to data from parliament's website. The tender was opened earlier on Thursday, according to a notice by the transport ministry published on the website of the Tenders Electronic Daily supplement to the Official Journal of the EU. According to the tender notice, the total estimated value of the contract is 3.9 billion euro. The deadline for submitting offers is October 22.BSP points to the airport's stable financial results and growing passenger traffic, along with an investment of over 900 million levs ($538.3 million/460.2 million euro) made in its infrastructure, as the main reasons to request a cancellation of the tender, a draft decision published on parliament's website shows.BSP also expects that the concessionnaire will cut staff and increase airport charges. In addition, BSP points out that Sofia Airport is a facility of strategic importance for the national security and operating it under a concession may have negative implications in this regard.