Bulgaria's transport ministry said it has again extended the deadline for submitting offers in the tender for awarding a 35-year concession contract to run Sofia international airport - by one week to February 5.The previous deadline was due to expire on January 29, the ministry said in an announcement last week. Tendering for the contract worth an estimated 3.9 billion euro ($4.6 billion) was launched in July with October 22 set as the original deadline for submitting offers. In October, the transport ministry extended the deadline by one month, to November 22. Subsequently, in November the transport ministry prolonged the bidding period once again, this time to January 29.The concession fee will carry the highest wеight in the procedure for selecting a concessionaire, of 55%. The remaining 45% will depend on the submitted development plan, business plan, financing plan, general strategy, traffic estimates and capital expenditure. The requirements for the potential candidates include having a net asset value of at least 200 million euro throughout the last three year and operating at least one international airport with an annual traffic of over 10 million passengers.