# SubStandard vs 737 CSFF

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.

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.

## The numbers

| Metric | SubStandard | 737 CSFF |
| --- | --- | --- |
| Price | **Free** | $2.99 |
| Rating | [5.0 (2 ratings)](https://appshunter.io/ios/app/substandard/id1513656520/reviews) | [5.0 (2 ratings)](https://appshunter.io/ios/app/737-csff/id1551516212/reviews) |
| Number of ratings | 2 | 2 |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 7 months | **Every 4 months** |
| Monetization | **Free** | Paid |
| Size | 33 MB | 11 MB |
| Requires iOS | **12.0** | 17.6 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Apple Watch |
| Age rating | 4+ | 4+ |
| Developer | [iService Ottner Röck](https://appshunter.io/developer/1413717324) | [Dan O'Leary](https://appshunter.io/developer/1177083778) |

## What reviewers say

### SubStandard

[App page](https://appshunter.io/ios/app/substandard/id1513656520)

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.

**Highlights:** Cold temperature corrections, Altitude set storage, Quick access to saved altitudes, Easy to use interface

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### 737 CSFF

[App page](https://appshunter.io/ios/app/737-csff/id1551516212)

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.

**Highlights:** 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

**In-app purchases:** none


## Frequently asked questions

### Is SubStandard free?

SubStandard is free to download, with no in-app purchases.

### Is 737 CSFF free?

737 CSFF costs $2.99, with no in-app purchases.

### Which has better reviews, SubStandard or 737 CSFF?

SubStandard and 737 CSFF are both rated 5.0 out of 5 on the App Store, from 2 and 2 ratings respectively.

### Do SubStandard or 737 CSFF have ads?

Neither SubStandard nor 737 CSFF shows ads.

### Which is updated more often, SubStandard or 737 CSFF?

SubStandard ships an update every 7 months, and 737 CSFF every 4 months. Most recently, SubStandard was updated on October 6, 2026 and 737 CSFF on October 7, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*