Commitments and Contingencies - Schedule of Firm Commitments (Details)	Sep. 30, 2024 aircraft_commitment aircraft
787
Long-term Purchase Commitment [Line Items]
Number of Firm Commitments \| aircraft_commitment	150
Contractual Aircraft Deliveries
Last Three Months of 2024	8
2025	18
After 2025	124
Expected Aircraft Deliveries
Last Three Months of 2024	3
2025	11
After 2025	136
737 MAX 8
Long-term Purchase Commitment [Line Items]
Number of Firm Commitments \| aircraft_commitment	18
Contractual Aircraft Deliveries
Last Three Months of 2024	18
2025	0
After 2025	0
Expected Aircraft Deliveries
Last Three Months of 2024	2
2025	16
After 2025	0
737 MAX 9
Long-term Purchase Commitment [Line Items]
Number of Firm Commitments \| aircraft_commitment	141
Contractual Aircraft Deliveries
Last Three Months of 2024	31
2025	40
After 2025	70
Expected Aircraft Deliveries
Last Three Months of 2024	3
2025	28
After 2025	110
737 MAX 10
Long-term Purchase Commitment [Line Items]
Number of Firm Commitments \| aircraft_commitment	167
Contractual Aircraft Deliveries
Last Three Months of 2024	0
2025	0
After 2025	167
Expected Aircraft Deliveries
Last Three Months of 2024	0
2025	0
After 2025	167
A321neo
Long-term Purchase Commitment [Line Items]
Number of Firm Commitments \| aircraft_commitment	115
Contractual Aircraft Deliveries
Last Three Months of 2024	14
2025	23
After 2025	78
Expected Aircraft Deliveries
Last Three Months of 2024	14
2025	23
After 2025	78
A321XLR
Long-term Purchase Commitment [Line Items]
Number of Firm Commitments \| aircraft_commitment	50
Contractual Aircraft Deliveries
Last Three Months of 2024	0
2025	0
After 2025	50
Expected Aircraft Deliveries
Last Three Months of 2024	0
2025	0
After 2025	50
A350
Long-term Purchase Commitment [Line Items]
Number of Firm Commitments \| aircraft_commitment	45
Contractual Aircraft Deliveries
Last Three Months of 2024	0
2025	0
After 2025	45
Expected Aircraft Deliveries
Last Three Months of 2024	0
2025	0
After 2025	45

Number Of Aircraft Contracted Delivery

No definition available.

Name:	ual_NumberOfAircraftContractedDeliveryAbstract
Namespace Prefix:	ual_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Aircraft To Be Delivered Under the Contract, Remainder of Year

+ References

No definition available.

+ Details

Name:	ual_NumberOfAircraftToBeDeliveredUnderTheContractRemainderOfYear
Namespace Prefix:	ual_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Aircraft To Be Delivered Under the Contract, Thereafter

+ References

No definition available.

+ Details

Name:	ual_NumberOfAircraftToBeDeliveredUnderTheContractThereafter
Namespace Prefix:	ual_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Aircraft To Be Delivered Under the Contract, Year One

+ References

No definition available.

+ Details

Name:	ual_NumberOfAircraftToBeDeliveredUnderTheContractYearOne
Namespace Prefix:	ual_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Aircrafts Expected To Take Delivery [Abstract]

+ References

No definition available.

+ Details

Name:	ual_NumberOfAircraftsExpectedToTakeDeliveryAbstract
Namespace Prefix:	ual_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Aircrafts Expected To Take Delivery, Remainder Of Year

+ References

No definition available.

+ Details

Name:	ual_NumberOfAircraftsExpectedToTakeDeliveryRemainderOfYear
Namespace Prefix:	ual_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Aircrafts Expected To Take Delivery, Thereafter

+ References

No definition available.

+ Details

Name:	ual_NumberOfAircraftsExpectedToTakeDeliveryThereafter
Namespace Prefix:	ual_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Aircrafts Expected To Take Delivery, Year One

+ References

No definition available.

+ Details

Name:	ual_NumberOfAircraftsExpectedToTakeDeliveryYearOne
Namespace Prefix:	ual_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermPurchaseCommitmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The minimum number of units that must be purchased, in connection with an unconditional purchase obligation that has not been recognized for financial reporting purposes.

+ References

No definition available.

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationMinimumQuantityRequired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_AircraftTypeAxis=ual_A787Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=ual_Boeing737MAX8Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=ual_Boeing737MAX9Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=ual_Boeing737MAX10Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=ual_AirbusA321neoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=ual_AirbusA321XLRMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=ual_AirbusA350Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: