# Assumptions & sources — Delta Starlink Cost

**Audience:** operators / researchers (the public UI does **not** link here — repo is private).
**Status:** All dollar figures on the site are **model estimates**, not audited airline fuel accounting.
**Last reviewed:** 2026-09-30
**Config file:** [`js/config.js`](js/config.js) — three scenarios (`best` / `average` / `worst`) plus Advanced sliders; default = `average`.

---

## What the counter measures

Extra jet-fuel **cost** attributable to flying older, higher-drag Ku/Ka / radome satcom antennas instead of a Starlink Terminal for Aviation–class low-profile ESA, on the share of Delta **mainline** flying hours that **could already have been** on Starlink if Delta had matched a United-like install pace.

A quieter secondary counter uses the **same extra gallons** × EPA Jet A CO₂ factor.

\[
\text{extra \$/day} = N_{\text{aircraft}} \times h_{\text{day}} \times f_{\text{Starlink}} \times g_{\text{extra}} \times p_{\text{JetA}}
\]

\[
g_{\text{extra}} = (\text{legacyPct} - \text{starlinkPct}) / 100 \times \text{baselineBurnGalPerHour}
\]

\[
\text{extra kg CO₂/day} = \text{extra gal/day} \times 9.75
\]

The displayed totals are the integral of those constant daily rates from `startDateISO` through now (tick ≈ 50 ms; whole dollars for $).

**Out of scope:** Delta Connection / regional fleet (325 aircraft in the same 10-Q), passenger revenue / NPS, install labor & STC, Leo vs Starlink commercial terms.

### Future v2 (not on the public homepage)

A later model could track actual Delta flights and daily Jet A prices; v1 intentionally uses a constant daily rate.

---

## Scenario table (defaults)

| | **Best** | **Average (default)** | **Worst** |
|--|----------|------------------------|-----------|
| \(N\) aircraft | 900 | **~1,000** (10-Q: 1,004) | 1,004 |
| \(h\) hours/aircraft/day | 8 | **10** | 12 |
| \(f\) counterfactual Starlink share | 0.20 | 0.30 | 0.45 |
| legacy / Starlink penalty % | 1.3 / 0.3 | 2.0 / 0.3 | 2.55 / 0.3 |
| baseline burn (gal/hr) | 800 | 800 | 800 |
| \(g\) extra gal/FH | **8.0** | **13.6** | **18.0** |
| \(p\) Jet A $/gal | 4.00 | 4.50 | 5.00 |
| **≈ $/day** | **~$46.1k** | **~$183.6k** | **~$488k** |
| **≈ t CO₂/day** | **~112** | **~398** | **~950** |
| Span vs best ($/day) | 1× | ~4× | ~10.6× |

Start window: `2026-03-30T00:00:00.000Z` (~6 months before 2026-09-30).

Slider ranges (Advanced panel) sit slightly beyond best/worst for exploration (e.g. N 750–1,200; h 6–14; f 5–60%; Jet A $3.25–5.75).

---

## Known vs assumed

| Input | Average value | Classification | Why |
|-------|---------------|----------------|-----|
| \(N\) mainline aircraft | ~1,000 (10-Q: 1,004) | **Known** | SEC Form 10-Q, period ended 2026-06-30 — mainline *operating* fleet = 1,004. Public UI displays ≈1,000. |
| Delta Starlink count | **0** | **Known** | No Starlink contract; Viasat/Hughes today; Amazon Leo ~500 aircraft from ~2028. |
| Jet A $/gal | 4.50 | **Known** (spot index) | Argus / Airlines for America U.S. Jet Fuel Index late Sep 2026 ~$4.42–4.53; default rounded to $4.50. |
| CO₂ factor | 9.75 kg/gal | **Known** | EPA GHG Emission Factors Hub — kerosene-type jet fuel. |
| Hours / aircraft / day | 10 | **Assumed** | Anchored to U.S. major **block-hour** utilization (~9–11); see FH/day research below. |
| Counterfactual Starlink fraction \(f\) | 0.30 | **Assumed** | Peer-pace proxy from United (official >400 by Jun 2026; tracker ~36% late Sep 2026). **Not** a claim Delta contracted Starlink. |
| Drag delta \(g\) | 13.6 gal/FH | **Assumed** (labeled estimate) | Derived from public Nicolls / Ryanair–Starlink Jan 2026 talking points. |

---

## Research notes (2026-09-30 pass)

### A) Flight hours / aircraft / day — is 10 reasonable?

**Short answer:** **Yes as a round mainline block-hour figure**; pure airborne (flight) hours for a mixed fleet run closer to ~8–9.5.

| Source | What it says | Block vs airborne |
|--------|--------------|-------------------|
| MIT Airline Data Project (BTS Form 41 Schedule T-2) | U.S. majors historically ~**9–11** average daily **block** hours per aircraft; Delta large-narrowbody airborne often ~**8.5–9.5** in later pre-pandemic years | Both reported |
| Airliners.net fleet discussion (2024 DL utilization) | A321neo **>12** hrs/day; mid types **6.5–9**; low-util hub feeders **<6.5**; A321ceo ~8–10.3 | Mostly utilization / block-like |
| Aviation Week Flight Friday (Jan 2024–Mar 2025) | Narrowbodies (~750) dominate cycles; widebodies (~160) ~8% of flights but ~¼ of **flight hours** (longer stages) | Flight hours emphasized for WB |

**Model choice:** average **10** FH/day (assumed), labeled as utilization closer to **block hours** than pure airborne. Best **8** / worst **12** bracket high-util narrowbodies and softer fleet averages. Visitors see a round number; ASSUMPTIONS keeps the block-vs-airborne caveat.

### B) United Starlink install count (lower bound + %)

| Claim | Number | As of | Source type |
|-------|--------|-------|-------------|
| Official hard lower bound | **>400** aircraft | 2026-06-22 | United MediaRoom / PR |
| Independent tracker | **607 / 1,669 ≈ 36%** | 2026-09-30 | unitedstarlinktracker.com |
| Earlier regional milestone | **>300** regional | 2026-02-02 | United / PR Newswire |

Use **>400** as the **known lower bound** in public copy; cite ~**600** / ~**36%** as the late-Sep reference for counterfactual \(f\) (mid case still uses conservative **30%**).

Sources:

- [United accelerates Starlink — MediaRoom, 2026-06-22](https://united.mediaroom.com/2026-06-22-United-Accelerates-Starlink-Wi-Fi-Rollout-with-First-Widebody-Transatlantic-Flight)
- [United PR — 300+ regional, Feb 2026](https://www.prnewswire.com/news-releases/united-spotlights-starlink-wi-fi-in-new-big-game-ad-as-airline-completes-installation-on-300-regional-aircraft-302676274.html)
- [United Starlink Tracker](https://unitedstarlinktracker.com/)

### C) Delta Starlink count = zero

Confirmed for the public site wording (“**none**,” not “essentially none”):

- Current IFC: **Viasat / Hughes** (Delta Sync / Hughes Fusion on select types) — **no Starlink**.
- Amazon Leo (ex–Project Kuiper): initial install on ~**500** aircraft beginning **~2028** (Delta News Hub / Reuters, Mar 2026).

Sources:

- [Delta / Amazon Leo announcement](https://news.delta.com/delta-amazon-leo-sign-agreement-deliver-next-era-connected-travel-and-digital-experiences)
- [Reuters — Amazon Leo × Delta](https://www.reuters.com/business/aerospace-defense/amazon-delta-team-up-in-flight-wi-fi-challenging-musks-starlink-2026-03-31/)
- [Hughes Fusion × Delta](https://www.hughes.com/resources/press-releases/delta-air-lines-selects-hughes-fusion-simultaneous-multi-orbit-flight)

### D) CO₂ emissions factor

**9.75 kg CO₂ per gallon** kerosene-type jet fuel (combustion / CO₂ only).

Source: [EPA GHG Emission Factors Hub](https://www.epa.gov/climateleadership/ghg-emission-factors-hub) (Table — Mobile Combustion CO₂; also in the 2024/2025 PDF hubs). Same factor used for the secondary emissions counter.

---

## Fleet & satcom context

### Mainline count — ≈1,000 (known; 10-Q = 1,004)

- Delta Air Lines Form 10-Q for the quarterly period ended **2026-06-30**: mainline operating fleet **1,004** aircraft. Regional (~325) is **out of scope**.
- Public UI displays **~1,000** (avoid “1,000–1,004” phrasing).
- Source: [SEC EDGAR — dal-20260630.htm](https://www.sec.gov/Archives/edgar/data/27904/000002790426000031/dal-20260630.htm)

### Counterfactual fraction — 30% mid (assumed)

- United began Starlink installs in **2025**.
- Average scenario uses **30%** as a conservative mid-window peer-pace proxy.
- Best 20% / worst 45% bracket that assumption.

---

## Drag / fuel burn delta

### Average — 13.6 gal/FH (assumed, derived)

Public January 2026 exchange (Ryanair vs Starlink / Michael Nicolls, Starlink VP Engineering):

| System | Stated fuel impact | Notes |
|--------|--------------------|-------|
| Legacy high-profile radome terminals | **~2%** | Public figure in the dispute |
| Starlink aviation terminal | **~0.3%** on 737-800 | Nicolls analysis |
| Baseline 737-class burn | **~800 gal/hr** | Same commentary |

\[
g = (2.0\% - 0.3\%) \times 800\ \text{gal/hr} = 13.6\ \text{gal/FH}
\]

Best uses 1.3% legacy → **8.0** gal/FH; worst uses 2.55% legacy → **18.0** gal/FH (same 0.3% Starlink and 800 gph baseline).

**Caveats:** public talking points / vendor analysis, not FAA certification drag polars for Delta’s exact Viasat/Hughes mix. Widebody vs narrowbody, aperture count, and fairing shape all move the real number. Treat \(g\) as a **labeled estimate**.

Sources:

- [Aerospace Global News — Musk vs O’Leary / fuel economics](https://aerospaceglobalnews.com/news/musk-vs-oleary-starlink-ryanair-wifi-costs/)
- [Benzinga — Starlink VP 0.3% claim](https://www.benzinga.com/news/space/26/01/49926178/starlink-adds-only-0-3-to-aircraft-fuel-burn-starlink-vp-says-elon-musk-eyes-further-cuts)
- [Aviation A2Z — Starlink / Ryanair fuel dispute](https://aviationa2z.com/index.php/2026/01/18/starlink-ryanair-spar-over-fuel-impact-of-in-flight-internet/)

---

## Jet A price

- **Airlines for America / Argus U.S. Jet Fuel Index** (wholesale airline-relevant): about **$4.42–4.53/gal** in late September 2026.
- Average default **$4.50**. Best $4.00 / worst $5.00 bracket the spot.
- Not FBO retail Jet-A. v1 uses a **constant** price per scenario.

Source: [Airlines for America — Argus U.S. Jet Fuel Index](https://www.airlines.org/dataset/argus-us-jet-fuel-index/)

---

## Worked examples

**Average (default):**

- Exposed FH/day = \(1000 \times 10 \times 0.30 = 3{,}000\)
- Extra gal/day = \(3{,}000 \times 13.6 = 40{,}800\)
- Cost/day ≈ \(40{,}800 \times 4.50 = \$183{,}600\)
- CO₂/day ≈ \(40{,}800 \times 9.75 / 1000 ≈ 398\) t

**Best:** \(900 \times 8 \times 0.20 \times 8.0 \times 4.00 = \$46{,}080\)/day

**Worst:** \(1004 \times 12 \times 0.45 \times 18.0 \times 5.00 = \$487{,}944\)/day

---

## How to revise

1. Edit scenario objects and `sliderRanges` in [`js/config.js`](js/config.js).
2. Keep `knownVsAssumed` flags honest when a primary source replaces a placeholder.
3. Update this file’s tables and links in the same change.
4. Bump `meta.lastReviewed`.
5. **Local only until Jason approves a push/deploy** — do not `git push` or `wrangler pages deploy` without explicit go-ahead. Do **not** link this file from the public `index.html`.