6.  PROPERTY, PLANT AND EQUIPMENT, NET

Property, plant and equipment are recorded at cost and depreciated over their useful lives. Maintenance and repair costs are expensed as incurred. Property, plant and equipment are as follows:

During the first quarter of 2025, the Company acquired Rahn, which included property, plant and equipment valued at $1.4 million.

During the first quarter of 2024, the Company acquired Heany, which included property, plant and equipment valued at $2.2 million. During the second quarter of 2024, the Company exercised a purchase option for the building and land from which CAD Enterprises, Inc. ("CAD") operates for $6.9 million, which was financed as described in the debt footnote (Note 7). During the third quarter of 2024, the Company acquired AIC, which included property, plant and equipment valued at $1.1 million.

During the second quarter of 2024, the Company issued 741 Class A Common Shares, valued at $30,011, to Air Power Dynamics, LLC in an arms-length exchange for an aerospace tooling machine. Air Power Dynamics, LLC, now Crawford Capital Enterprises, LLC, is controlled by Ambassador Edward Crawford, who is the chairman of the Company's board of directors. 

Depreciation expense was $727,191 and $624,750 for the three months ended June 30, 2025 and 2024, respectively, and $1,458,387 and $1,304,708 for the six months ended  June 30, 2025 and 2024, respectively.