SubStandard vs 737 CSFF
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
SubStandard
This aviation utility app simplifies applying cold temperature corrections for altitudes. It allows users to save frequently used altitude sets for rapid retrieval, enhancing efficiency in flight planning.
- Cold temperature corrections
- Altitude set storage
- Quick access to saved altitudes
- Easy to use interface
Read full descriptionHide full description
SubStandard is an easy to use app to apply cold temperature corrections in aviation. Moreover, it lets you store sets of altitudes for quick access later on.
737 CSFF
A visual guide to understanding Cold Soaked Fuel Frost (CSFF) on 737 aircraft wings. It references airline handbooks and Boeing FCOM guidance for educational purposes.
- Visual representation of CSFF scenarios
- Study guide for 737 wing frost
- References North American Airline Flight Handbook
- Includes Boeing FCOM guidance
- Educational tool for pilots
Read full descriptionHide full description
This app is a study guide and a visual representation to aid in the understanding around the many scenarios when Cold Soaked Fuel Frost (CSFF) is encountered on the wing of a 737. This app is not approved for use during flight operations. The CSFF guidance in this app is designed around a North American Airline Flight Handbook and reference to the Boeing FCOM. This app is not a substitute for company flight manuals, an FAA approved deicing program, Boeing FCOM guidance or good judgement.
Screenshots
Verdict
The clearest difference is price: SubStandard at Free against 737 CSFF's $2.99. SubStandard also leads on iOS requirement (12.0 vs 17.6). On rating, ratings volume, update cadence and ads there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
SubStandard is free to download; 737 CSFF costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.
On the App Store both sit at effectively the same score — 5.0 for SubStandard against 5.0 for 737 CSFF. Both are backed by a comparable volume of ratings — 2 and 2 respectively.
SubStandard ships an update every 7 months, 737 CSFF every 4 months. The most recent releases landed on October 6, 2026 and October 7, 2026 respectively.
| Parameter | SubStandard | 737 CSFF |
|---|---|---|
| Price | Free — better | $2.99 |
| Rating | 5.0 (2 ratings) | 5.0 (2 ratings) |
| Positive reviews | 0.0% of reviews | — |
| Number of ratings | 2 | 2 |
| Update frequency | Every 7 months | Every 4 months — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free — better | Paid |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Apple Watch |
| Requires iOS | 12.0 — better | 17.6 |
| Further details — not scored | ||
| Size | 33 MB | 11 MB |
| Age rating | 4+ | 4+ |
| Developer | iService Ottner Röck | Dan O'Leary |
Customer experience
SubStandard
737 CSFF
In-app purchases
SubStandard
No in-app purchases
737 CSFF
No in-app purchases
