A day-by-day plan
One timeline the whole group is looking at, built out of the things a trip is actually made of rather than a generic list of events.
Seven kinds of thing, each with its own fields
A flight, a stay, transport, an activity, a meal, free time, or something custom. A flight carries a flight number, terminals, a booking reference and a fare class; free time carries neither a booking nor a price. The rules are enforced on the server, so the shape of an item is never a matter of who typed it.
Every event in the time zone where it happens
Each item stores an instant plus the zone of the place it happens in, and renders there — not on your phone's clock. A flight leaving Manila at 23:40 and landing 05:15 in Tokyo lands on the correct local day for everyone reading it.
Your day, or the trip's day
The same timeline, filtered to the items you are actually on. Useful the moment a group splits up for an afternoon and half of it is on a different boat.
Rooms and beds
Assign people to rooms on an accommodation item, with capacities enforced and anyone still unassigned shown plainly. Each room carries a cost weight that can propose the split for that booking — propose, never apply. Who sleeps where is a rooming decision; who pays what stays a money decision.
More than one destination
A trip can run Manila → Cebu → Siargao as legs with their own dates, instead of being flattened into a single place and a single date range.
Leaves the app when it has to
Export the plan as a calendar file or a PDF, or hand someone a read-only link. The friend meeting you at the airport does not need an account, and is not installing anything.
Survives losing signal
The itinerary is cached on the device, and edits made offline are queued and replayed when the connection comes back — rather than being lost, or silently overwriting someone else's change.
Sail your trip.
Start a trip, invite the group, and put the first flight on the timeline.