Aircraft Co-Ownership: Spreadsheets vs. Apps

You bought an airplane with a partner. Congratulations — you just cut your fixed costs in half and doubled the number of scheduling conflicts in your life.

Most co-ownership groups start with a predictable set of DIY tools. They work. For a while.

The DIY Approach

Here’s what a typical co-ownership setup looks like after six months:

Scheduling usually starts as a tab on the shared spreadsheet — a calendar grid where you type your name into cells. That gets frustrating quickly, so most groups graduate to a shared Google Calendar or Outlook calendar. Now everyone can see bookings on their phone. It’s a real improvement — but the calendar is completely disconnected from everything else. There’s no link between “I had the airplane Saturday” and “here are my tach times and what I owe.”

Cost management lives in a shared Google Sheet or Excel file. Date, tach out, tach in, pilot name. Monthly formulas calculate what each person owes. This works until someone enters tach times out of order and everything downstream is wrong. Or until the person who built the formulas goes on vacation and nobody else understands them.

Maintenance is another tab on that same spreadsheet — a list of items with due dates that someone needs to manually check and update. It works until the oil change is 20 hours overdue because nobody looked at the tab in three weeks.

Communication is whatever the group already uses — a group text, a WhatsApp thread, maybe email. Someone finds a small oil leak during preflight and texts the group. The other partner is in a meeting and doesn’t see it for three hours.

There’s nothing wrong with any of this in principle. These tools are free, familiar, and flexible. The problem is that each one operates in isolation, and the glue holding them together is human discipline.

Where DIY Breaks Down

The Tach Problem

This is the big one. Every shared aircraft needs an unbroken record of engine tach time. It’s how you track flight hours, calculate bills, and know when maintenance is due.

In a spreadsheet, tach continuity depends on every pilot entering their exact tach out and tach in values, in order, without gaps or overlaps. One transposed digit and everything downstream is wrong. Finding the error means scrolling through months of entries comparing each row to the next.

A purpose-built app solves this by auto-populating tach out from the previous flight’s tach in. You only enter tach in. The system maintains continuity automatically, and if you need to edit a past flight, it cascades the change through all subsequent flights.

The Scheduling-to-Billing Gap

With a shared Google Calendar, you know who had the airplane. But someone still has to go back to the spreadsheet, look up the tach times, cross-reference the calendar, and calculate the monthly bill. The calendar and the spreadsheet don’t talk to each other.

A dedicated app connects these automatically. Log a flight with your tach times and the calendar booking it came from, and the estimated monthly bill updates in real-time. No cross-referencing required.

The Communication Problem

Someone finds a discrepancy during preflight and texts the group chat. But texts get buried under other conversations. There’s no severity level, no persistent record, and no guarantee everyone sees it before their next flight.

With a squawk reporting system, the issue is logged with a severity level. If it’s serious enough to ground the airplane, every partner sees a red alert the next time they open the app. There’s no way to miss it.

The Maintenance Problem

A spreadsheet can tell you when maintenance is due — if someone remembers to check it. But it can’t send you an alert when the transponder cert is expiring next week. It can’t color-code items by urgency. And it can’t automatically recalculate the next oil change based on when you completed the last one.

The Currency Problem

Are you current to carry passengers? When does your medical expire? When was your last flight review?

Most co-ownership groups don’t track pilot currency at all — each pilot is expected to manage that on their own. An app calculates your currency automatically from the flights you log — day landings, night landings, instrument approaches — and warns you before anything expires.

When to Switch

Not every co-ownership group needs an app. If you and one partner fly the same airplane from the same airport, rarely have scheduling conflicts, and one of you genuinely enjoys maintaining the spreadsheet — keep doing what works.

But consider switching when:

• You add a third partner and the shared calendar starts getting confusing
• Tach discrepancies keep showing up and nobody can figure out where
• The monthly billing spreadsheet takes more than 5 minutes or depends on one person who built it
• Maintenance items have slipped through the cracks more than once
• You’ve ever had a “I didn’t know you had it booked” moment despite having a shared calendar
• You’re tired of the gap between your calendar, your spreadsheet, and your group text

The transition is painless — most apps let you import your existing flight history from a CSV and start tracking from there. Your shared calendar doesn’t go away — it gets replaced by one that’s connected to everything else.

The Cost Comparison

The app costs less than a quart of oil per member per month. The question isn’t whether you can afford it — it’s whether you can afford the time and errors you’re currently absorbing for free.

Bottom Line

The DIY approach — shared calendars, spreadsheets, and group texts — is a perfectly reasonable starting point. These tools are free, everyone knows how to use them, and they get the job done for small groups.

But they don’t talk to each other. The calendar doesn’t know about tach times. The spreadsheet doesn’t know about maintenance. The group text doesn’t have severity levels. And the person doing the monthly billing is doing manual work that software can eliminate.

If your co-ownership group has outgrown the DIY setup — or if you’re just starting out and want to skip the duct-tape phase entirely — a purpose-built app pays for itself in time saved and errors avoided.

5-by-5 is built specifically for aircraft co-ownership groups and flying clubs. See how it works or start for free.