During the six months ended September 30, 2021, the increase in the Company’s goodwill primarily related to the acquisitions of the remaining 51% interest in Euro Infrastructure Co. and of RigNet on April 30, 2021 (see Note 12 – Acquisitions for more information) and an insignificant effect of foreign currency translation recorded within all three of the Company’s segments. During the six months ended September 30, 2020, the increase in the Company’s goodwill related to the effects of foreign currency translation recorded within all three of the Company’s segments.

Other acquired intangible assets are amortized using the straight-line method over their estimated useful lives of two to 12 years (which approximates the economic pattern of benefit). Amortization expense related to other acquired intangible assets was $7.4 million and $1.3 million for the three months ended September 30, 2021 and 2020, respectively, and $13.3 million and $2.9 million for the six months ended September 30, 2021 and 2020, respectively.

The expected amortization expense of amortizable acquired intangible assets may change due to the effects of foreign currency fluctuations as a result of international businesses acquired. The current and expected amortization expense for acquired intangible assets for each of the following periods is as follows:

	Amortization
	(In thousands)
For the six months ended September 30, 2021	$	13,328

Expected for the remainder of fiscal year 2022	$	14,966
Expected for fiscal year 2023		29,935
Expected for fiscal year 2024		28,371
Expected for fiscal year 2025		26,252
Expected for fiscal year 2026		26,100
Thereafter		117,707
	$	243,331

In the first quarter of fiscal year 2022, the gross amount and accumulated amortization for acquired identifiable intangible assets were reduced by the retirement of fully amortized assets that were no longer in use.