Source: https://guthlabs.ai/docs/instruments/layover-connection-time-checker/implementation/

instrument implementation / implementation-contract

# Layover Connection Time Checker implementation

A source-bound implementation contract for Layover Connection Time Checker; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-105

**Effect**: Computation or source lookup only

## Input and validation requirements

The checker is vulnerable to two specification hazards: an overnight connection can change from a valid 45-minute connection to an invalid negative duration if date-rollover conventions are interpreted differently, and excessively large timestamp values can lose one minute through unsafe integer precision. It also cannot produce authoritative results without a dated, airline- and airport-specific MCT table.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "connecting_airport": "LHR",
    "arrival_timestamp": "2025-06-14T10:00:00Z",
    "departure_timestamp": "2025-06-14T11:30:00Z",
    "arrival_flow": "domestic",
    "departure_flow": "international",
    "arrival_terminal": "T2",
    "departure_terminal": "T5"
  },
  "expected_outputs": {
    "layover_minutes": 90,
    "mct_minutes": 90,
    "buffer_minutes": 0,
    "meets_mct": true
  },
  "reference_data": {
    "mct_row": {
      "airport": "LHR",
      "arrival_flow": "domestic",
      "departure_flow": "international",
      "arrival_terminal": "T2",
      "departure_terminal": "T5",
      "mct_minutes": 90
    },
    "source_convention": "widely tabulated standard value for common published MCT test fixtures; airport/airline dated guidance must be verified"
  },
  "working": "Both timestamps are already UTC. Layover = 11:30 - 10:00 = 1 hour 30 minutes = (1 x 60) + 30 = 90 minutes. Buffer = 90 - 90 = 0 minutes. Since 90 >= 90, the connection passes."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/layover-connection-time-checker/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/layover-connection-time-checker/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/layover-connection-time-checker/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`