Airport Operating Revenue

As an enterprise fund, the airport relies on revenues from airlines to support its operations, maintenance needs, and capital projects. Without adequate controls in place to ensure billing and other financial processes are accurate and effective, the airport cannot ensure it collects all airline revenue in a timely manner.

FINDING 1 – Billing process weaknesses result in overbilling and uncollected revenue

• Weaknesses in the airport's billing process resulted in inaccurarries, which led to overbilling and uncollected revenue. We identified invoices where the airport overbilled airlines by almost $6 million.
• Contract payment terms were not enforced. We estimated invoices from two reviewed airlines from 2022 through 2024 should have incurred $1.6 million in interest penalties from late payments.

FINDING 2 – Operations do not align with policies and procedures

Operations did not align with polices and procedures. Inadequate policies and procedures negatively impacted the effectiveness of several reviewed processes, including leased-space inspections, gate-use monitoring, the year-end settlement process, and billing adjustments.

1.1 Improve accuracy of gate-use billing – Denver International Airport’s senior vice president of accounting should ensure the department creates and implements policies and procedures for coordinating, calculating, and reviewing gate-use invoices. These policies and procedures should be reviewed, updated, and finalized annually to ensure amounts billed are correct and processes are followed consistently. Once finalized, the department should ensure appropriate staff are trained on these updates annually.

Denver International Airport – Agree, Implementation Date – Aug. 31, 2026

1.2 Update gate-billing procedures – Denver International Airport’s senior vice president of airline and commercial affairs should ensure the department’s policies and procedures for gate billing are updated annually, aligning with contract requirements. Gate-billing practices should also be reviewed, updated, and published annually to ensure documented policies are current.

After implementing changes to policies and procedures, the airport should also ensure all stakeholders and relevant staff are aware of changes made to gate-billing procedures by notifying airlines and providing training to staff. Billings should also be reviewed for accuracy and to confirm staff’s compliance with changes.

Denver International Airport – Agree, Implementation Date – Sept. 30, 2026

1.3 Align procedures for late payments with contract requirements – Denver International Airport’s senior vice president of accounting should enforce the airport’s contract terms to charge airlines interest on late payments. 

Denver International Airport – Agree, Implementation Date – Dec. 31, 2026

1.4 Develop procedures to apply year-end credits – To prevent large lingering credits on accounts, Denver International Airport’s chief financial officer should coordinate the airport’s Finance Division to develop, document, and implement procedures to include credit application to outstanding balances as part of the year-end settlement.

Denver International Airport – Disagree

2.1 Revise inspection procedures and monitor inspections – Denver International Airport’s senior vice president of airline and commercial affairs should:

• Revise procedures to include current inspection processes to confirm whether airlines are using only agreed-upon leased spaces.
• Ensure inspection procedures include sufficient detail, identifying information to include with inspections reports.
• Determine whether the inspection form includes all necessary inspections steps and whether the form should still be included with inspection reports.
• Ensure procedures include sufficient detail on expected inspection follow-up activities.
• Identify documentation needed to demonstrate an airline and relevant airport department resolved inspection.
• Provide airlines and relevant airport departments with a copy of the report after inspections.
• Ensure monitoring processes confirm inspections and follow-up activities to identify whether inspection findings have been resolved. 

Denver International Airport – Agree, Implementation Date – Sept. 30, 2026

2.2 Update gate-use policies and procedures – Denver International Airport’s senior vice president of airline and commercial affairs should ensure the department updates its gate-monitoring policies and procedures, ensuring it gives sufficient, specific details on effective gate-monitoring steps and covers all relevant department practices and processes.

Denver International Airport – Agree, Implementation Date – July 31, 2026

2.3 Review rates and charges settlement procedures – Denver International Airport’s senior vice president of financial planning should establish a regular review schedule to confirm or update year-end settlement procedures to ensure settlement reports are accurate and complete. This review should be completed before beginning the year-end settlement process for that year to accurately reflect any changes to cost centers or exhibits.

Denver International Airport – Agree, Implementation Date – Sept. 30, 2026

2.4 Revise accounting procedures – Denver International Airport’s senior vice president of accounting should ensure processes are documented in accounting procedures to outline when and how billing adjustments for airline space changes are handled and entered in PROPworks after the date of the change.

Denver International Airport – Agree, Implementation Date – Aug. 31, 2026 

Auditor’s addendum to agency response for Recommendation 1.4

We know the use and lease agreement distinguishes between year-end adjustment credits and airline revenue-sharing credits and may limit the airport in how certain credits are applied. However, the recommendation is not intended to alter the use and lease agreement requirements. Rather, our recommendation was made to ensure the airport establishes documented procedures to identify, track, communicate, and resolve credits with those requirements and in a timely manner.

At the time of our audit, unapplied credits for United and Frontier accounts totaled $13.7 million, with some credits outstanding for over eight years. We also found there were still outstanding credits every year from 2017 through 2025. As outlined in our report, the presence of these credits creates an unnecessary ongoing administrative burden for the airport. The credits remaining unapplied for multiple years shows that processes do not consistently result in timely resolution, regardless of the credit type.

To ensure that these credits are applied in a timely manner, airport managers should work with stakeholders to update and document practices to enable the airport to more quickly obtain information from airlines, helping the airport better decide how the adjustment and revenue sharing credits should be applied.