Charter Hire Expenses
Charter hire expenses for the vessels chartered in from third parties were $9.2 million and $4.1 million for the six months ended September 30, 2020 and 2019, respectively. The increase of $5.1 million, or 124.7%, was caused by an increase in time chartered-in days, which increased from 153 for the six months ended September 30, 2019 to 376 for the six months ended September 30, 2020.
Vessel Operating Expenses
Vessel operating expenses were $38.8 million during the six months ended September 30, 2020, or $9,644 per vessel per calendar day, which is calculated by dividing vessel operating expenses by calendar days for the relevant time-period for the technically-managed vessels that were in our fleet. Vessel operating expenses per vessel per calendar day increased by $1,320 from $8,324 for the six months ended September 30, 2019 to $9,644 for the six months ended September 30, 2020. The increase in vessel operating expenses for the six months ended September 30, 2020, when compared with the six months ended September 30, 2019, was primarily the result of a $5.6 million, or $1,390 per vessel per calendar day, increase in operating expenses related to repairs and maintenance, spares and stores, and coolant costs, which is inclusive of an increase of $2.4 million, or $602 per vessel per calendar day, in operating expenses related to the drydocking of vessels including repairs and maintenance, spares and stores, coolant costs, and other drydocking related operating expenses.
General and Administrative Expenses
General and administrative expenses were $17.2 million for the six months ended September 30, 2020, an increase of $4.6 million, or 36.3%, from $12.6 million for the six months ended September 30, 2019. This was driven by increases of $1.9 million in annual cash bonuses to certain employees, $1.3 million in salaries, wages and benefits, $0.6 million in higher insurance premiums, and $0.6 million in legal and professional fees, which is largely a result of costs incurred in our transition from being an emerging growth company under the Jumpstart Our Business Startups Act.
Interest and Finance Costs
Interest and finance costs amounted to $15.8 million for the six months ended September 30, 2020, a decrease of $3.2 million, or 17.1%, from $19.0 million for the six months ended September 30, 2019. The decrease of $3.2 million during this period was due to a decrease of $5.2 million in interest incurred on our long-term debt, primarily resulting from a decrease in LIBOR rates and a reduction of average indebtedness, partially offset by an increase of $1.8 million in amortization of deferred financing fees, mainly due to accelerated amortization of $2.1 million related to the refinancing of the Cresques and the refinancing of the Original Commercial Tranche during the six months ended September 30, 2020. Average indebtedness, excluding deferred financing fees, decreased from $699.9 million for the six months ended September 30, 2019 to $666.6 million for the six months ended September 30, 2020. As of September 30, 2020, the outstanding balance of our long-term debt, net of deferred financing fees of $11.8 million, was $634.5 million.
Unrealized Gain/(Loss) on Derivatives
Unrealized gain on derivatives was $3.5 million for six months ended September 30, 2020, compared to an unrealized loss $6.7 million for the six months ended September 30, 2020. The favorable $10.2 million difference is primarily attributable to an increase of $8.7 million in favorable fair value changes to our interest rate swaps resulting from changes in forward LIBOR yield curves and an increase of $1.5 million in favorable changes to our FFA positions.
Realized Gain/(Loss) on Derivatives
Realized loss on derivatives was $2.9 million for the six months ended September 30, 2020, compared to a realized gain of $1.7 million for the six months ended September 30, 2019. The unfavorable $4.6 million change is primarily attributable to (1) decreases in floating LIBOR resulting in a $3.7 million unfavorable variance on realized losses in the current period on our interest rate swaps and (2) unfavorable settlements of $0.9 million on our FFA positions.