increase in product margin of $4.7 million and an increase in service margin of $1.0 million. As a percentage of revenue, gross margin increased to 44% from 42%. The increase in gross margin percentage was primarily due to an increase in the proportion of product sales to total revenue and a favorable mix.
Income from operations for the second quarter of fiscal 2021 was $13.9 million, an increase of $5.8 million from the second quarter of fiscal 2020 of $8.1 million. The increase in income from operations was primarily a result of an increase in gross margin of $5.7 million and a decrease in selling, general and administrative (“SG&A”) expense of $1.3 million, partially offset by an increase in research and development (“R&D”) expense of $1.1 million.
Other income, net, for the second quarter of fiscal 2021 was $0.2 million, as compared to $1.4 million for the second quarter of fiscal 2020. The decrease in other income, net was primarily due to a decrease in interest income resulting from a decrease in the average interest rate earned on our investment portfolio.
Provision for income taxes for the second quarter of fiscal 2021 was $2.5 million, as compared to $1.1 million for the second quarter of fiscal 2020. The increase in provision for income taxes was primarily due to the increase in income before income taxes combined with an increase in the projected fiscal year 2021 effective tax rate.
Equity method investment loss, net of tax, for the second quarter of fiscal 2021 was $9.5 million, as compared to $0.9 million for the second quarter of fiscal 2020. Equity method investment loss, net of tax, for the second quarter of fiscal 2021 included a loss of $8.4 million for our proportionate share of the HAPSMobile Inc. joint venture’s impairment of its investment in Loon LLC.
Net income attributable to AeroVironment for the second quarter of fiscal 2021 was $2.1 million, as compared to $7.5 million for the second quarter of fiscal 2020. The second quarter of fiscal 2021 included the impairment loss of $8.4 million related to HAPSMobile Inc.’s investment in Loon LLC.
Earnings per diluted share attributable to AeroVironment for the second quarter of fiscal 2021 was $0.09, as compared to $0.31 for the second quarter of fiscal 2020. The second quarter of fiscal 2021 included the impairment loss of $8.4 million related to HAPSMobile Inc.’s investment in Loon LLC.
Non-GAAP earnings per diluted share was $0.48 for the second quarter of fiscal 2021, as compared to $0.34 for the second quarter of fiscal 2020.
FISCAL 2021 YEAR-TO-DATE RESULTS
Revenue for the first six months of fiscal 2021 was $180.1 million, an increase of 6% from the first six months of fiscal 2020 revenue of $170.2 million. The increase in revenue was due to an increase in service revenue of $9.2 million and an increase in product sales of $0.7 million.
Gross margin for the first six months of fiscal 2021 of $76.3 million was consistent with the first six months of fiscal 2020. Gross margin for the first six months of fiscal 2021 reflected a decrease in product margin of $4.4 million, partially offset by an increase in service margin of $4.2 million. As a percentage of revenue, gross margin decreased to 42% from 45%. The decrease in gross margin percentage was primarily due to a decrease in the proportion of product revenue to total revenue and an unfavorable product mix.
Income from continuing operations for the first six months of fiscal 2021 was $26.2 million, a decrease from the first six months of fiscal 2020 of $26.9 million. The decrease in income from continuing operations was primarily a result of an increase in R&D expense of $3.5 million, partially offset by a decrease in SG&A expense of $2.9 million.
Other income, net, for the first six months of fiscal 2021 was $0.4 million, as compared to other income, net of $3.1 million for the first six months of fiscal 2020. The decrease in other income, net was primarily due to a decrease in interest income resulting from a decrease in the average interest rate earned on our investment portfolio.