Aerospace and safety-critical parts can't be cut open to check for internal defects, which is exactly the problem nondestructive testing solves. The common NDT methods compared, and what ASNT certification levels actually mean.
ASNT doesn’t actually certify most NDT technicians directly —
SNT-TC-1A is an employer-based program, meaning the employer, not
ASNT, formally certifies its own technicians against guidelines ASNT
publishes. That distinction surprises people expecting a
test-and-credential system like a typical professional certification.
Nondestructive Testing (NDT) covers a family of inspection methods
that evaluate a part’s integrity without damaging or destroying it —
critical for aerospace and safety-critical components where you can’t
simply cut a sample part open to check for internal defects. Common
methods include ultrasonic testing (UT), magnetic particle testing
(MT), liquid penetrant testing (PT), radiographic testing (RT), and
visual testing (VT), each suited to different defect types and material
conditions.
| Level | Typical role |
|---|---|
| Level I | Performs specific calibrations, tests, and evaluations under supervision, following documented procedures |
| Level II | Sets up and performs tests, interprets and evaluates results, organizes and reports results |
| Level III | Develops procedures, interprets standards, and has overall responsibility for the NDT program at a facility |
Level I and II certification happens through the employer’s own
written practice, built around ASNT’s SNT-TC-1A recommended guidelines
— this is why “SNT-TC-1A certified” really means “certified by an
employer following ASNT’s recommended practice,” not a credential ASNT
issues directly. Level III certification runs differently, through
ASNT’s Central Certification Program (ACCP), which aligns with the
international ISO 9712 standard.
Because Level I and II certification is employer-administered, the
actual rigor of a “certified” technician can vary meaningfully between
companies — a customer qualifying a new supplier’s NDT capability needs
to review that supplier’s written practice, not just take “SNT-TC-1A
certified” at face value as a uniform credential. This is exactly the
kind of detail that shows up during a Nadcap NDT task group audit.
NDT is one of the special-process task groups Nadcap accredits,
which means a shop performing NDT for aerospace customers often needs
Nadcap accreditation for that specific process on top of a compliant
SNT-TC-1A written practice — see our related guide on
Nadcap
accreditation for how process-specific accreditation works
alongside a broader quality certification like AS9100.
NDT certification itself isn’t a standalone course in SCMEP’s
current catalog — Level I and II certification runs through an
employer’s written practice, and Level III through ASNT’s own ACCP
program. What we do offer is the quality systems foundation these
processes sit inside; see our AS9100
Overview. As a NIST Manufacturing Extension
Partnership affiliate serving South Carolina manufacturers since
1989, our focus is connecting NDT program quality to the broader
aerospace supplier qualification process.
If your shop is building or auditing an NDT written practice, you
can browse the Quality and Inspection
training catalog or email the training team.
Not for Level I and II. SNT-TC-1A is an employer-based program — the employer certifies its own technicians against guidelines ASNT publishes. Level III certification does run directly through ASNT’s Central Certification Program (ACCP).
Ultrasonic testing (UT), magnetic particle testing (MT), liquid penetrant testing (PT), radiographic testing (RT), and visual testing (VT) are common methods, each suited to different defect types and material conditions.
Level I performs specific tests under supervision, Level II sets up and interprets tests independently, and Level III develops procedures and holds overall responsibility for a facility’s NDT program.
NDT is one of the special-process task groups Nadcap accredits. An aerospace supplier performing NDT often needs Nadcap accreditation for that specific process in addition to a compliant SNT-TC-1A written practice.
