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Fair Value Measurements
 3 Months Ended
Mar. 31, 2026
Fair Value Disclosures [Abstract]  
Fair Value Measurements Fair Value Measurements
The Company applies the provisions of Accounting Standards Codification (“ASC”) 820, Fair Value Measurement, which defines a single authoritative definition of fair value, sets out a framework for measuring fair value and expands on required disclosures about fair value measurements. The provisions of ASC 820 relate to financial assets and liabilities as well as other assets and liabilities carried at fair value on a recurring and nonrecurring basis. The standard clarifies that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the standard establishes a three-tier value hierarchy, which prioritizes the inputs used in measuring fair value as follows:
Level 1Unadjusted quoted prices in active markets for identical assets or liabilities accessible to the reporting entity at the measurement date.
Level 2Other than quoted prices included in Level 1 inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability.
Level 3Unobservable inputs for the asset or liability used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date.
The carrying amounts of the Company’s cash, accounts payable, accrued compensation, and accrued liabilities approximate their fair values due to the short-term nature of these instruments.
The following table presents information about the Company’s assets and liabilities that are measured at fair value on a recurring basis as of March 31, 2026 and December 31, 2025 and indicate the fair value hierarchy of the valuation inputs the Company utilized to determine such fair value (in millions):
As of March 31, 2026
As of December 31, 2025
DescriptionLevel 1Level 2Level 3Level 1Level 2Level 3
Assets:
Cash and cash equivalents:
Money market funds$790.2 $— $— $883.3 $— $— 
Short-term investments:
U.S. Treasuries
601.3 — — 703.8 — — 
Corporate debt securities
— 223.5 — — 239.4 — 
Other current assets
Option to acquire FBO
— — 44.8 — — 44.8 
Total assets measured at fair value
$1,391.5 $223.5 $44.8 $1,587.1 $239.4 $44.8 
Liabilities:
Warrant liabilities
Public warrants
$4.9 $— $— $19.9 $— $— 
Private placement warrants
— — 2.2 — — 10.0 
Total liabilities measured at fair value
$4.9 $— $2.2 $19.9 $— $10.0 
Short-term Investments
The Company’s short-term investments consist of high quality investment grade marketable securities and are classified as available-for-sale. The Company classifies its investments in U.S. Treasury securities as Level 1 because they are valued using quoted market prices in active markets. The Company classifies its investments in corporate debt securities as Level 2 because they are valued using inputs other than quoted prices which are directly or indirectly observable in the market, including readily available pricing sources for the identical underlying security which may not be actively traded.
The following table presents a summary of the Company’s cash equivalents and short-term investments as of March 31, 2026 (in millions):
As of March 31, 2026
DescriptionAmortized CostUnrealized GainsUnrealized LossesFair Value
Cash and cash equivalents:
Money market funds$790.2 $— $— $790.2 
Short-term investment
U.S. Treasuries
603.4 — (2.1)601.3 
Corporate debt securities
224.5 — (1.0)223.5 
Total$1,618.1 $— $(3.1)$1,615.0 
The following table presents a summary of the Company’s cash equivalents and short-term investments as of December 31, 2025 (in millions):
As of December 31, 2025
DescriptionAmortized CostUnrealized GainsUnrealized LossesFair Value
Cash and cash equivalents:
Money market funds$883.3 $— $— $883.3 
Short-term investment
U.S. Treasuries
704.6 — (0.8)703.8 
Corporate debt securities
239.9 — (0.5)239.4 
Total$1,827.8 $— $(1.3)$1,826.5 
The unrealized losses related to the Company’s short-term investments were primarily due to changes in interest rates and not due to increased credit risk or other valuation concerns. The Company had no other-than-temporary impairments for the three months ended March 31, 2026 and 2025.
Public Warrants
The measurement of the public warrants as of March 31, 2026 is classified as Level 1 due to the use of an observable market quote in an active market under the ticker “ACHR WS”. The quoted price of the public warrants was $0.28 and $1.15 per warrant as of March 31, 2026 and December 31, 2025, respectively, with changes in fair value recognized in the condensed consolidated statements of operations.
Private Placement Warrants
The Company utilizes a Monte Carlo simulation model for the private placement warrants at each reporting period, with changes in fair value recognized in the condensed consolidated statements of operations. The estimated fair value of the private placement warrant liability is determined using Level 3 inputs. Inherent in a Monte Carlo simulation model are assumptions related to expected volatility, expected exercise term, risk-free interest rate, and dividend yield.
The key inputs into the Monte Carlo simulation model for the private placement warrants are as follows:
InputMarch 31,
2026		December 31,
2025
Stock price$5.17$7.52 
Strike price$11.50$11.50
Term (in years)0.460.71
Risk-free rate3.7 %3.5 %
Volatility97.1 %89.1 %
Dividend yield0.0 %0.0 %
The following table presents the change in fair value of the Company’s Level 3 private placement warrants liability during the three months ended March 31, 2026 (in millions):

Balance as of December 31, 2025
10.0 
Change in fair value(7.8)
Balance as of March 31, 2026
$2.2 
In connection with the change in fair value of the Company’s private placement warrants liability, the Company recognized a gain of $7.8 million and $17.0 million during the three months ended March 31, 2026 and 2025, respectively, within other income (expense), net in the condensed consolidated statements of operations. Refer to Note 12 - Warrants for additional information about the private placement warrants.
Option to Acquire FBO
In connection with the acquisition of Hawthorne Airport as defined below in Note 6 - Business Combinations, on December 8, 2025, the Company recorded an option to acquire a 75% ownership interest in the fixed-base operator (“FBO”) business operating at the airport for an exercise price of $25.0 million. The option is measured at fair value using a Black-Scholes model, with changes in fair value recognized in other income (expense), net in the condensed consolidated statements of operations, and is classified as a Level 3 fair value measurement.
During the three months ended March 31, 2026, there was no material change in the fair value of the option. The option was classified within other current assets in the condensed consolidated balance sheets as it was exercisable prior to December 31, 2026. The option was subsequently exercised and the acquisition was closed on April 1, 2026. Refer to Note 17 - Subsequent Events for additional information.
The key inputs into the Black-Scholes model for the option to acquire FBO business are as follows:
As of
InputMarch 31,
2026		December 8,
2025
Strike price (in millions)
$25.0 $25.0 
Term (in years)0.01
0.2
Risk-free rate3.7 %3.8 %
Volatility64.0 %50.0 %
Dividend yield0.0 %0.0 %
Financial Instruments Not Recorded at Fair Value on a Recurring Basis
Certain financial instruments, including debt, are not measured at fair value on a recurring basis in the condensed consolidated balance sheets. The fair value of debt as of March 31, 2026 approximates its carrying value (Level 2). Refer to Note 8 - Debt for additional information.
Assets and Liabilities Recorded at Fair Value on a Non-Recurring Basis
Certain assets and liabilities are subject to measurement at fair value on a non-recurring basis if there are indicators of impairment or if they are deemed to be impaired as a result of an impairment review.