The phrase "altered plan" is correct and usable in written English.
You can use it when referring to a plan that has been changed or modified from its original version.
Example: "Due to unforeseen circumstances, we had to implement an altered plan for the project timeline."
Alternatives: "revised plan" or "modified plan".
The government has altered Plan A quite a bit, it's not really recognisable in its original form..
By 1965, the mayor announced his renewed support, offering a slightly altered plan that submerged parts of the expressway complex, as well as a proposal for some new housing as a sop to relocated residents.
These documents indicate that an altered plan had been finally agreed upon on 20th March, 1940, a convoy should leave England on 5th April, and that mining in Norwegian waters would begin the same day; and that on 5th April the sailing time had been postponed until 8th April.
Update: Due to a "crush of interest", Striebeck has posted on a slightly altered plan for feedback tomorrow.
More generally, throughout the experiment there was a decrease in fission rate, with an increased probability of the appearance of abnormally dividing cells with an altered plan of cell division or asymmetric divisions.
Scott often altered plans too, leaving little margin for error.
They altered planning norms and focused on different measures of performance.
The threat has mostly altered plans of friends and family members who expected to go to Rio to cheer them.
This experiment was designed to learn if there are hemispheric asymmetries in the control of altered plans of actions.
And in 1993, when Microsoft decided to build its own on-line service, the Microsoft Network, it was beset by false starts, name changes, and altered plans.
The letter cited the governor's altered plans for the system along with California's inability to match the federal funds as grounds for terminating the award.
